Wikipedia:Reference desk/Science

Welcome to the science section
of the Wikipedia reference desk.

skip to bottom

Select a section:

• Computing
• Entertainment
• Humanities
• Language
• Mathematics
• Science
• Miscellaneous
• Archives

Want a faster answer?

Main page: Help searching Wikipedia

   

How can I get my question answered?

• Select the section of the desk that best fits the general topic of your question (see the navigation column to the right).
• Post your question to only one section, providing a short header that gives the topic of your question.
• Type '~~~~' (that is, four tilde characters) at the end – this signs and dates your contribution so we know who wrote what and when.
• Don't post personal contact information – it will be removed. Any answers will be provided here.
• Please be as specific as possible, and include all relevant context – the usefulness of answers may depend on the context.
• Note:
  • We don't answer (and may remove) questions that require medical diagnosis or legal advice.
  • We don't answer requests for opinions, predictions or debate.
  • We don't do your homework for you, though we'll help you past the stuck point.
  • We don't conduct original research or provide a free source of ideas, but we'll help you find information you need.

Ready? Ask a new question!

How do I answer a question?

Main page: Wikipedia:Reference desk/Guidelines

• The best answers address the question directly, and back up facts with wikilinks and links to sources. Do not edit others' comments and do not give any medical or legal advice.

See also:

• Teahouse
• Help desk
• Village pump
• Help manual

March 16

Possible causes for temporary blindness due to car crash

Rest assured I`m not asking for the dreaded medical advice, it is for short story I`m writing for school. I need to know if there is any kind of traumatic injury (after say crashing car head on in a tree or a metal pole) that would cause temporary blindness and doctors would be almost certain the induvidual will recover fully stright away ~~Xil (talk) 03:51, 16 March 2011 (UTC)

It would be possible, impact to the optic nerves or part of the brain. Graeme Bartlett (talk) 04:42, 16 March 2011 (UTC)

Yes, but why - hemorrage (I suspect that would rather cause something similar to stroke), inflamation or what? ~~Xil (talk) 06:45, 16 March 2011 (UTC)

This paper cites a study into 10 patients with blunt trauma injuries (mostly caused by crashes) that caused blindness (14 eyes in all, I assume some suffered blindness in both eyes, other only in one). It says that in most cases the blindes was caused by swelling of the optic nerve, but also stated that in three cases a fracture in the optic canal wall was the cause of blindness. [1]. I must admit that I have only read the brief summary, but that alone seems to provide a useful basic insight into your question. Darigan (talk) 12:35, 16 March 2011 (UTC)

Judging by the summary those aren`t cases of temoprary blindness (it makes it quite clear that patients needed medical intervention to spare their vision). For this case, I need patient to expierience emotional trauma, which makes him rethink purpose of life, not have lasting damage. Just something that would sound pausible, I don`t want to write about something that would kill him in reality ~~Xil (talk) 14:17, 16 March 2011 (UTC)

Anything that could cause blindness is likely to have a high chance of being fatal without medical treatment. Having his eyesight restored by medical treatment should work for your story. --Tango (talk) 01:43, 17 March 2011 (UTC)

It is not question of receiving medical help or not, it`s just that I don`t want major brain surgery in the story. I need doctors saying that the problem will sort itself out in few weeks and patient freaking out at chance that doctors might be wrong. Such conditions exist outside of realm of soap operas? ~~Xil (talk) 13:52, 17 March 2011 (UTC)

Which salt water, with a lot of salt or little salt, absorbs heat more quickly?

I may be not looking at answers — Preceding unsigned comment added by Like sushi (talk • contribs) 04:16, 16 March 2011 (UTC)

At a given temperature, the thermal conductivity of salt water decreases with increasing salinity.[2] Red Act (talk) 17:55, 16 March 2011 (UTC)

Thank you.Like sushi (talk) 02:42, 17 March 2011 (UTC)

Real E.T. or Hoax

Is this news real ?  Jon Ascton  (talk) 04:39, 16 March 2011 (UTC)

Yeah, right. 75.57.242.120 (talk) 04:54, 16 March 2011 (UTC)

Mierda del toro... --Jayron32 05:18, 16 March 2011 (UTC)

My poor uncle. -- Toytoy (talk) 05:57, 16 March 2011 (UTC)

Yes, that's really "news" (unfortunately). But you don't really think it's about a real baby alien, do you? WikiDao ☯ 16:16, 16 March 2011 (UTC)

remote controlled helicopter

Is there such a thing as a remote controlled helicopter, basically a regular helicopter with servos connected to the controls? Could they rig some up in a hurry over there in Japan, to overfly those reactors and dump stuff on them without irradiating human pilots? Just wondering. 75.57.242.120 (talk) 04:50, 16 March 2011 (UTC)

Dumping stuff on them wouldn't do much, it would just roll off. The outer container is not very hot, it's the internal one that is, so they need to pump water inside. That said, they certainly can do it remote if necessary. But it's not necessary - the radiation is still pretty low, so a regular fire-fighting helicopter could overfly, dump, and continue and be exposed to almost nothing. Ariel. (talk) 06:04, 16 March 2011 (UTC)

Could they rig some up in a hurry? No, aircraft modifications are not undertaken lightly, and especially not the sort of modification required to convert a conventional heavy-lift helicopter into an un-manned helicopter. A modification project of this kind would involve design, manufacture of parts for the modification, installation of the parts, and then extensive testing and fine-tuning, mostly at light weights. Then there would need to be testing and fine-tuning at heavy weights. It couldn't be done in the sort of time-frame that would interest the people grappling with the Japanese reactor problems. Dolphin (t) 06:24, 16 March 2011 (UTC)

They would use these: Helicopter bucket, they already exist (if Japan doesn't have any I'm sure they could be brought). No need for any time consuming design. Ariel. (talk) 09:31, 16 March 2011 (UTC)

Thanx. I know that Chernobyl liquidator helicopter pilots (they dumped concrete over the burning reactor) got considerable radiation exposure and I think some of them died of related illnesses. That's why I asked about remotes. The R/C helicopter article is about little tiny models that don't count for this, though they might be good for photography, sensors, etc. Also I wonder if the USS Reagan (aircraft carrier off Japan) has any UAV's (Predators or whatever) on board. Yeah, Dolphin51 is probably right about modification, even though there is a 30 km no-fly zone around the reactor right now, so I'd think they could suspend normal aviation rules. I wasn't thinking of any fancy stuff designed specially for the helicopter, just some servos or off-the-shelf industrial robot arms, bolted into the pilot's seat and operating the controls. This doesn't seem terribly hard to do with automobiles but I can see how aircraft could be more complicated. 75.57.242.120 (talk) 07:21, 16 March 2011 (UTC)

Re dumping stuff: they are talking about using fire hoses to shoot water into the hole in the roof of the building that exploded, to refill the spent fuel pool which has been boiling from decay heat. Apparently it is exposed from above. 75.57.242.120 (talk) 07:23, 16 March 2011 (UTC)

Actually they are dumping stuff already (can't find a RS but it was on the news in the past 30 mins or so and also mentioned on BBC's twitter [3]) even if they ruled it out a few hours ago [4] [5] perhaps a reminder in an ongoing crisis where things can change rapidly it's wise to be carefully when saying something like 'they won't do that' or 'that won't happen'. Note on BBC it does according to NHK TV "the helicopter can't stay too long over the plant because of the risk of radiation to the crew" Nil Einne (talk) 08:20, 16 March 2011 (UTC)

Well, remotely operated helicopters seem potentially useful for firefighting and other unsafe activities, so even if they can't be built soon enough to deal with this nuclear incident, maybe they're something the aircraft makers could work on. 75.57.242.120 (talk) 10:30, 16 March 2011 (UTC)

There are already helicopter-style UAVs such as the Northrop Grumman MQ-8 Fire Scout. However, they don't seem to have the lifting capacity of manned helicopters yet. --Colapeninsula (talk) 11:15, 16 March 2011 (UTC)

Latest news now of course is that the plans were abandoned due to fears of radioactive contamination for the crew Nil Einne (talk) 12:01, 16 March 2011 (UTC)

The radiation levels are rising and falling as things change at the plant. You might see a burst of radiation as a steam vent opens, causing the crew to evacuate, then have the wind blow the steam out to sea, causing the radiation levels to fall and letting the crew return. --Carnildo (talk) 20:12, 16 March 2011 (UTC)

I haven't read anything suggesting the helicopters will be back. Edit: Should have taken my own advice [6]. (I admit even when posting the first time I was suprised no one was talking about trying again later but since I still never heard anything I decided there must have been something I was missing.) Even so it still demonstrates the idea that there was no reason to use a remote controlled helicopter seems to have been incorrect. Nil Einne (talk) 21:56, 16 March 2011 (UTC)

I'm disappointed. I would have thought that sometime during the Cold War the U.S. military would have thought up a way to radiation-proof a helicopter. I suppose we're probably just as badly prepared for a nuclear war as we would be for a disaster like this. Wnt (talk) 00:06, 17 March 2011 (UTC)

Radiation-proofing a helicopter would basically involve lining it with thick sheets of lead. That is very heavy - not a good thing in an aircraft. You would also need to make it air-tight and fit appropriate ventilation systems. While all of that could be done, it would make the helicopter extremely inefficient when operating away from radiation. Building helicopters for use only in high-radiation situations would be very expensive for fairly small gain. The gain right now would be quite big, but situations like this one are extremely rare. --Tango (talk) 01:39, 17 March 2011 (UTC)

Hmmm - so you think the limits on the helicopter are truly from direct radiation exposure and not from the contamination of personnel through the air? I'd assumed otherwise (I was just thinking you could seal it and filter the air thoroughly) but I don't actually know. Wnt (talk) 06:53, 17 March 2011 (UTC)

Thanks,the Fire Scout is the kind of thing I was wondering about. I wonder why they're not using them. It does look like they've sent some fixed-wing drones.[7] 75.57.242.120 (talk) 00:47, 17 March 2011 (UTC)

Because as per Colapeninsula they're puny things which couldn't deliver significant amounts of water presuming they could be reliable fitted to lift any water? (Probably because they weren't intended to lift things.) It also sounds like they don't have many and are still basically in testing. Nil Einne (talk) 04:46, 17 March 2011 (UTC)

According to the link you provide, the drone in question is the Northrop Grumman RQ-4 Global Hawk. It's got a payload capacity of 3000 pounds, but it's entirely internal storage. Even if you could refit it to carry a water bucket, that's only about 300 gallons, which would have essentially no impact. --Carnildo (talk) 23:19, 17 March 2011 (UTC)

The Global Hawk was used for recon, IR photography etc. Wasn't suggesting using it for water. The way to use the Fire Scout would probably be to lower one end of a hose into the building, and bring the other end to a safe distance away so water can be pumped through it. It now looks like they're doing something like that with a construction crane instead. They have also got some mobile robots on the way, which seems like it's about time. I wonder if this incident will speed development of remote-operated heavy equipment in general, such as cargo helicopters. 75.57.242.120 (talk) 08:22, 19 March 2011 (UTC)

Question about light clocks/ time dilation?

Let we have the following three clocks in a spaceship which is moving close to the speed of light.

Clock 1 is AB long which is perpendicular to the direction of ship. Clock 2 is CD and Clock 3 is EF long. Both 2 &3 are along the direction of spaceship such that 3 is just above No.2. Distance between A&B, C&D and E&F is L = distance covered by a light in one second. 

Now in order to analyze time dilation for one second a pulse is fired at the same time from 

From A towards B in Clock 1

From back of the ship "C" to it's  front "D" in Clock 2

From the front of the ship "E" to it's  back "F" in Clock 3 

For inside observer: 

Clock1- experienced a perpendicular of the right angle triangle of time dilation diagram. 

Also a pulse fired from the back of the ship to the front would take the same amount of time as a pulse fired from the front to the back. 

For outside observer:

Clock1-observed  a hypotenuse of right angle of time dilation and hence experienced more time than inside observer for the same clock.

Clock2- observed a very small fraction of distance covered by a pulse due to the high speed of ship in the same direction. Thus experiencing more more more and more time than inside observer for the same clock.(so slow even if length contraction is ignored)

Clock3- notice a very short time due to the rushing of back of ship and hence experienced a less time as compared to inside observer. This means time is contracting in this case for him (so fast even if length contraction is added)

So are their differences wrong?74.198.150.229 (talk) 06:34, 16 March 2011 (UTC)khattak#1-420

The one-way times are all different, as you noticed, but the round-trip times are all the same. -- BenRG (talk) 08:57, 16 March 2011 (UTC)

(ec)You hit onto one of the fundamental consequences of the Theory of Relativity, namely that there is no global simultaneity. The order of events (and hence, possibly, causality!) depends on the frame of reference of the observer. Our article on relativity of simultaneity has more. In other words, an observer in the middle of the space ship who shoots light beams at mirrors in the front and the back will observe them hitting the walls at the same time. A outside observer not co-moving with the ship will see the front and the back beam hit at different times. --Stephan Schulz (talk) 09:01, 16 March 2011 (UTC)

Here's a link to that article: Relativity of simultaneity Red Act (talk) 09:33, 16 March 2011 (UTC)

I don't want discuss it further because I know the wikipedia rules but sounds like I didn't explain things clearly enough for you understand my question therefore it behooves me to try it the other way.

Let we have the following arrangement.

Mirror at the back of ship is B, Mirror at the middle of ship is M, Mirror at the front of ship is F

For on board observer pulses are back and forth in between BM and FM at the same time. Each cycle is same for him. Cycle means back and forth distance covered by pulse in either BM or FM.

Let study the two cycle of aforementioned pulses for outside observer not co- moving.

Cycle 1

Between B&M- pulse would hit B very early and then reflected very very slowly towards M

Between M&F- Pulse would be moving very slowly towards F and will be reflected towards M when it hit F. 

Since for onboard observer, cycle 1 is completed earlier than outside observer and for him pulses are ready again towards B &F while for outside observer cycle1 is yet to be completed. So here is my question?

Why would outside observer see two pulses in between B&M (one which is lag behind for him in cycle1and other from cycle2 of onboard observer) and similarly two pulses between F&M. 

This means number of pulses increases per cycle ( of on board observer) for outside observer if he had the opportunity to observe all.  So is this parallax for out side observer who is not co-moving? 74.198.150.229 (talk) 18:38, 16 March 2011 (UTC)khattak#1-(ec)

It seems to me that you are failing to distinguish the time as measured by one observer from the time as measured by the other observer when you say "Since for onboard observer, cycle 1 is completed earlier than outside observer". These are different times measured by different observers and it makes no sense to say that one happens earlier than the other. Dauto (talk) 19:53, 16 March 2011 (UTC)

The reasons why I'm thinking eccentrically is that if we fired a pulse from the back of spaceship towards its front then onboard observer will see a pulse leave a ship through it's front in one second (if the length of the ship is one light second) while an outside observer will find it in very slow motion inside ship because both a pulse  and a ship are moving almost at the same speed. Therefore for him a pulse would take hours hours ...... to reach the front of ship.

Therefore to me it sounds like round trip wouldn't be same for both observers because ship and a pulse are almost at the same speed if traveling in same direction. This is my last reponse to this question therefore pls don't consider this for warning. Thanx —Preceding unsigned comment added by 74.198.150.213 (talk) 22:44, 16 March 2011 (UTC)

The round trip won't last the same for both observers. It will be time dilated for the external observer. I don't think the wikipedia police will come knocking at your door if you chose to post one more response to that question. Dauto (talk) 23:39, 16 March 2011 (UTC)

With respect to the moving frame, the distance between the mirrors is L/γ, where γ is the relativistic gamma factor ($1/{\sqrt {1-v^{2}/c^{2}}}$). The time for the light to cross this distance moving with the ship is ${\frac {L}{\gamma \,(c-v)}}$, which is large if v ≈ c. The time for it to cross in the other direction is ${\frac {L}{\gamma \,(c+v)}}$. The sum of these is

${\Bigg (}{\frac {L}{\gamma }}{\Bigg )}{\frac {(c-v)+(c+v)}{(c+v)(c-v)}}={\frac {2L}{\gamma \,c\,(1-v^{2}/c^{2})}}=\gamma {\frac {2L}{c}},$

which is γ times the round-trip time in the rest frame. -- BenRG (talk) 00:58, 17 March 2011 (UTC)

Cooling the inside of the building

About Japanese nuclear accident.

Wouldn't it help to cool it down with liquid nitrogen and oxygen?

If the supression pool is broken, though hopefully not, it would work more.

I may not be looking at answers. — Preceding unsigned comment added by Like sushi (talk • contribs) 07:30, 16 March 2011 (UTC)

Liquid oxygen is best kept away from nuclear reactors - or, for that matter, barbeque grills!^[8] Supposedly, if you soak the charcoal with oxygen before lighting, you can even get a sizeable explosion. Liquid nitrogen would be very cold, but it doesn't actually have as much heat capacity as water, so there's not so much of an advantage ... though it would put out a fire. Wnt (talk) 08:00, 16 March 2011 (UTC)

Sorry, I seem to have forgotten to write the most important.

I would say the air inside the building to be replaced with mixture of liquid nitrogen and oxygen. — Preceding unsigned comment added by Like sushi (talk • contribs) 08:30, 16 March 2011 (UTC)

I mean, in evaporated form. — Preceding unsigned comment added by Like sushi (talk • contribs) 08:42, 16 March 2011 (UTC)

Er you mean oxygen and nitrogen gas? Nil Einne (talk) 09:01, 16 March 2011 (UTC)

I fail to see how it would be diffrent from mix of oxygen and nitrogen 84.52.26.118 (talk) 09:06, 16 March 2011 (UTC)

I suppose so.

If it is generated from liquid nitrogen and oxygen, it would be still very cold, I think. — Preceding unsigned comment added by Like sushi (talk • contribs) 09:05, 16 March 2011 (UTC)

In case it's not clear, the air inside the building, not the pressure vessel. — Preceding unsigned comment added by Like sushi (talk • contribs) 09:41, 16 March 2011 (UTC)

On second thought, if the suppression pool is broken, the water in the pool may freeze, and the effect of it, I do not know. — Preceding unsigned comment added by Like sushi (talk • contribs) 09:58, 16 March 2011 (UTC)

I don't think that is likely. I don't actually understand what you think is going to happen but you still have the problem Wnt mentioned of little heat capacity. It's even worse now since you don't even have much of it. It seems a bad idea to try to have a highly pressured mixtured in the containment vessel for many reasons. So presuming you're keeping it atmospheric that means you end up with ~ 1.3kg/cubic metre. I don't know the volume of the containment vessel but even if it's 1000 cubic metres that's only 1300kg you're putting in, a relatively tiny amount of a lower heat capacity then water substance. Plus the heat isn't even going to transfer well. Not to mention if you're talking about the spent fuel storage pond isn't one of the problems that they're now exposed to air? Are you planning to replace the earth's atmosphere with 'evaporated liquid nitrogen and oxygen'? Nil Einne (talk) 10:58, 16 March 2011 (UTC)

Looking at Heat capacity#Table of specific heat capacities,

although columns for Volumetric heat capacity are left blank,

in "mol"-related columns, which seems to have something to do with volume,

"Water at 100C (steam)" is, in value, only less than 1.5 times than that of nitrogen and oxygen.

Heat transfer#Convection says "Convection is usually the dominant form of heat transfer in liquids and gases.",

and mentions Newton's law of cooling, "The rate of heat loss of a body is proportional to the difference in temperatures between the body and its surroundings."

If the temperature of 'evaporated liquid nitrogen and oxygen' is so close to absolute zero,

I think we can assume at least additional 300C difference in temprature

(, assuming steam of water to be over 100C),

and if (the body's temperature - temperature of steam of water) is smaller than

2/3 of (the body's temperature - temperature of 'evaporated liquid nitrogen and oxygen')

I don't think there isn't a chance.

And I don't know if the buildings' state is so bad to let the vapor

(of water or of nitrogen and oxygen) easily out. — Preceding unsigned comment added by Like sushi (talk • contribs) 13:42, 16 March 2011 (UTC)

It seems like you intend to replace air with very cool air? Perhaps using liquid nitrogen in air conditioner would work somewhat better - probably you can keep it from evaporating that way ~~Xil (talk) 13:56, 16 March 2011 (UTC)

I don't know what suggestion "using liquid nitrogen in air conditioner" is,

but if it is to bring a lot of air conditioners to the site, it seems to take a lot. — Preceding unsigned comment added by Like sushi (talk • contribs) 14:18, 16 March 2011 (UTC)

I think the point you are missing is that the objective is not just to cool the fuel rods, but to *keep them* cool - they are continually generating heat. So you need a constant supply of coolant. Water is a good coolant because it has a high heat capacity by volume, good thermal conductance and is readily available in large quantities - which, ironically, is why reactors are often built near the coast. Gandalf61 (talk) 14:09, 16 March 2011 (UTC)

I think keeping the temperature of the air (or vapor) inside the building as low as 0C,

wouldn't hurt, except for ones working in it,

because water doesn't freeze at 0C, if containing a little salt. — Preceding unsigned comment added by Like sushi (talk • contribs) 14:57, 16 March 2011 (UTC)

No matter how much salt you add, you can only lower the freezing point a dozen or two degrees...LN2 temperatures will quickly freeze it either way, during which the volume will expand for a while and likely break various vessels containing it. That's...bad. I think you are missing the truly enormous scale of the situation. Even though LN2 temperature is very low, a gas at that temperature is simply not good at cooling the huge amount of solid and liquid high-temperature materials. And once it does warm up, it no longer helps--in fact it would have to be continually replaced because the reactor components are not just "hot" but are "continuously generating more heat". If you put ice cubes in a pan in a hot oven, they will melt and cool the pan. But if the oven is on, the pan will still get hot, boiling away the water (heating the coolant solid -> liquid -> gas -> hot gas) and now you have...nothing except the same hot pan where you started. DMacks (talk) 15:31, 16 March 2011 (UTC)

The last comment was not about cooling the air (or vapor) to near absolute zero,

but to 0C.

I didn't think in a way that just inside the building is as highly pressured as the inside of the pressure vessel,

so, at least then, didn't have reason to think pushing away the air (or vapor) with colder (or cooler) one hurts. (Again, except for ones who are working in it.) — Preceding unsigned comment added by Like sushi (talk • contribs) 16:08, 16 March 2011 (UTC)

No, that is not what I meant, you may want to explore how air conditioner works, but esentialy my idea is that you would have pipes filed with liquid nitrogen, rather than releasing it in the buliding where it would evaporate and escape the building (unless it is hermeticaly sealed, which seems unrealistic) ~~Xil (talk) 16:33, 16 March 2011 (UTC)

This seems bold, but do you mean by "pipe", the pipe in which primary coolant is?

(I do not know if there is secondary coolant)

No, I mean, instead of filling room with nitrogen and oxygen (note that it is what air is made of, so once it evaporates all you will get is somewhat cooler air), you would have piping filled with constantly liquid nitrogen, which would cool the air around it ~~Xil (talk) 01:11, 17 March 2011 (UTC)

Would it transfer heat, I mean, coldness as quickly as by making it a vapor?

If the pipe is directly made in contact with the body, it would work very well.

Making it in vapor can be done from relatively far from the body, for the safety,

and doing both, though with less efficiency, would work more

Like sushi (talk) 01:40, 17 March 2011 (UTC)

Pipes, can they be soaked into glue-ish substance for making it possible to stick to the body, even if thrown from far apart?

(It may be a silly idea, though)

Like sushi (talk) 01:56, 17 March 2011 (UTC)

Per the above discussion, one of the plans was to try to dump water from a helicopter. Another one is/was? to shoot water from a police or fire water canon. I think it's clear such a structure is not going to keep air/oxygen/nitrogen/water vapour/whatever in very well... Nil Einne (talk) 21:55, 16 March 2011 (UTC)

At least at the time it was constructed, the building seems to have been meant to serve as one of the sealing in emergency.

Like sushi (talk) just before 23:42, 17 March 2011 (UTC)

I'm confused now. Are you suggesting they should have kept it with an evaporated liquid nitrogen/oxygen atmosphere all the time? I thought the question was how to cool it right now since they were clearly not having a problem cooling it before the current problems and you specifically mentioned the nuclear accident and in the specific post I was replying to you said 'And I don't know if the buildings' state is so bad to let the vapor' (which was in reply to me saying 'they're now exposed to air' although I admit now exposed to the atmosphere was what I was intending). BTW can you please sign your posts with four tildes ~~~~ to avoid confusion. Nil Einne (talk) 23:42, 16 March 2011 (UTC)

I just don't know how much the building is damaged, and if all the buildings are damaged, I mentioned the intention at the time of construction to suggest, if the damage is not all over, it may still serve for a little goodLike sushi (talk) 00:35, 17 March 2011 (UTC)

There are pics in the article on the accident, quite obviously walls and roof are gone ~~Xil (talk) 01:14, 17 March 2011 (UTC)

Most of the relevant buildings have recently exploded, so I think it is safe to say they are significantly damaged! --Tango (talk) 01:32, 17 March 2011 (UTC)

It looks at least 3 and 4 plants have no roof nor wall, by the picture.

Like sushi (talk) 01:40, 17 March 2011 (UTC)

I may be just becoming so desperate, so take this with a bunch of salt.

Would berrying the reactors in a lot of (presumably iron or steel) pachinko balls help?

As iron or steel seems to have high thermal conductivity,

and it would still leave (small, but not no) room for water to enter,

and would enlarge the surface area of matters with relatively high temperature

(because heat capacity of iron or steel is small),

which may make it easy for pumped water to deprive heat.

(Even if it seems so nice, do not jump on it, everyone,

it wouldn't take many people to check this idea.)

Like sushi (talk) 05:34, 17 March 2011 (UTC)

Explanation: I am thinking in a way like,

pachinko balls may "take away" heat

from relatively small surface area of container vessel (?)

to relatively large suface area of the balls

more quickly than air (or vapor) does.

(Though air is gas and flows freely, so I am losing hope in it,

and anyway, I don't have a way to even personally judge which is better)

Like sushi (talk) 05:59, 17 March 2011 (UTC)

what happens if signal peptidase malfunctions and fails to cleave the signal sequence?

Does it usually hinder the function of the produced protein? John Riemann Soong (talk) 08:38, 16 March 2011 (UTC)

Well, it depends by what you mean "function". The (endoplasmic reticulum) signal peptide is a transmembrane domain, and the protein isn't going anywhere without some kind of cleavage. (I should add, though, that signal peptidase has quite a few homologues, and the options for cleavage by various enzymes at various points can become complicated - things like amyloid precursor protein can be cut in many ways, with significant effects) But if you just want protein activity, it isn't uncommon for a tethered protein to work the same way as an untethered one. But any individual protein may have its own quirks. Wnt (talk) 15:10, 16 March 2011 (UTC)

Flocking birds in SE England

A large flock of European starling in England

In the last couple of days I've noticed at least two large flocks of birds wheeling about the sky, here in south-east england.

Would they be flocking because they've just arrived (from Scandinavia, Europe, Africa?) Or are they preparing to leave (to Scandinavia, Europe, Africa?) Or is it impossible to tell? Is it possible infer anything else about these flocks or birds? Thanks 92.29.117.90 (talk) 13:02, 16 March 2011 (UTC)

Any bird species in particular? Given that it is spring they probably were wintering in England and now are prepering to migrate to north ~~Xil (talk) 13:39, 16 March 2011 (UTC)

Sorry I was too far away to identify them. How can you telling they are departing rather than arriving? Thanks. 92.29.117.90 (talk) 13:48, 16 March 2011 (UTC)

I believe there is no need for them to flock when arriving, they would rather spread out once they are close to the destination. Assuming, of course, that they flock because of migration, not some other reason ~~Xil (talk) 14:08, 16 March 2011 (UTC)

Perhaps European starling - see image. Although the sight is becoming less common as bird numbers decrease, this is a well known but poorly understood feature of starling behaviour. More information here. Ghmyrtle (talk) 13:49, 16 March 2011 (UTC)

PS: Starling flocking has nothing to do with migration. Ghmyrtle (talk) 14:55, 16 March 2011 (UTC)

Here in south central UK starlings are still wheeling about in huge murmurations before settling to roost for the night. If memory serves they will reduce in size pretty soon as they start nesting but will be back at it again in the autumn. Richard Avery (talk) 16:24, 16 March 2011 (UTC)

Does that mean they are not preparing to migrate, but are British starlings who behave like that during the winter? Dosnt flocking make it difficult for them to find enough food? Thanks 92.15.26.91 (talk) 20:49, 16 March 2011 (UTC)

Flocking in birds etc, and similar behaviours (schooling in fish and other marine organisms, herding, swarming - I notice our articles on these subjects could use some improvement) is thought to some extent (and variably with each case) to be a protection against predators. Each individual flock member decreases its chances of being predated by surrounding itself with many other targets, and some predators are confused by an over-profusion of targets.

Starlings and similar birds tend to exhibit this behaviour more in the winter months when food is scarcer and 'following the flock' may increase the chances of finding at least some food, which may also tend to be concentrated in small areas like recently harvested, ploughed or sown fields, of stands of seeding trees etc, and when they are not competing for nesting places. In the spring and summer the wider and more plentiful availability of food enables them to disperse and stake their own more individual nesting and foraging territories. Other bird species pursue other strategies, there being several viable niches in the environment. {The poster formerly known as 87.81.230.195} 90.197.66.165 (talk) 22:38, 16 March 2011 (UTC)

A good video here. Alansplodge (talk) 03:12, 19 March 2011 (UTC)

Arrow of time

I was watching a BBC programme (Wonders of the Universeand the presenter was talking about the arrow of time. He seemed to say that time goes in one direction but nobody knows why. How would you know if time was reversed and if time doesn't continually head in one direction would it even matter? --BlackberryPicking (talk) 13:03, 16 March 2011 (UTC)

If direction of time reversed, the entropy of the universe will tend to decrease with time. i.e. heat will flow from cooler bodies to hotter bodies. Generally the energy of the universe(which is conserved regadless of the direction of time) will be concentrated in fewer particles over time. Diwakark86 (talk) 13:54, 16 March 2011 (UTC)

That's a silly program. There is really no mystery about the time's arrow. It is a tricky thing but it is well understood. To answer your question, don't you think you would notice a river flowing up river and then raining backwards into the sky while you got younger over the years like Benjamin Button? Dauto (talk) 13:46, 16 March 2011 (UTC)

Entropy is the reason for the arrow of time I believe. That programme, like so much on evening TV, seems designed for kids or young teenagers in its vocabluary, intellect, slow delivery, and its new-information/waffle quotant. (Television presenters should model themselves upon Patrick Moore in my opinion). I don't think you would notice any theorectical reversals in time as your brain would be reversing as well. 92.29.117.90 (talk) 13:52, 16 March 2011 (UTC)

I watched the program in question and it was actually reasonably good. (Brian Cox has appeared on The Sky At Night, if that improves his credibility with you!) It is a difficult concept to get your head around, so it isn't surprising that someone wouldn't understand it the first time it was presented to them, however good that presentation would be. --Tango (talk) 15:17, 16 March 2011 (UTC)

Agreed. There is no great mystery about the arrow of time. Percieved time goes in the direction of increaisng entropy, by definition. You cannot remember the future because memory (either biological or non-biological) involves observing a current state (which includes the memory) and infering another state which we call the "past" - but the inferred state must be one with lower entropy than the present, otherwise there are too many "choices" to make an inference. Therefore the perceived past must, by definition, have a lower entropy than the present. In a universe with constant entropy there could be no memories, and hence no perceived past or direction of time. In other words, asking why time never goes backwards is like asking why things never fall upwards. See Entropy (arrow of time) for more details. Gandalf61 (talk) 13:59, 16 March 2011 (UTC)

The arrow of time considered in isolation doesn't make much sense. Time doesn't really have a direction. Time just is. When people talk about the arrow of time, they are relations between different things that give time a direction. The most obvious one is human memory. We remember the past, we don't remember the future ("the pyschological arrow of time"). You then try and explain why other things go in the direction they do, relative to the psychological arrow. For example, why, when we see a broken egg do we often remember it when it was intact but, when we see an intact egg we never remember it when it we broken? It all comes down to the concept on entropy, which is what Brian Cox spent most of that program talking about. The universe started out in a highly ordered state (we don't really know why) and statistics tells us it must be becoming steadily more and more disordered. Both storing memories and breaking eggs increase the disorder in the universe, so they happen in the same direction.

The idea of reversing the direction of time doesn't make much sense. You can change all the t's in your equations to -t's, but that won't actually change much (see T-symmetry). You can define time to be going in the opposite direction, but that just means you would remember what you define to be the future rather than what you define to be the past, so your perceptions wouldn't actually change (you would still remember intact eggs, not broken ones).

--Tango (talk) 15:17, 16 March 2011 (UTC)

The arrow of time article (distinct from entropy (arrow of time) covers the various definitions. Musing over the arrow of time became popular with Stephen Hawking, I think his A Brief History of Time. Wnt (talk) 15:26, 16 March 2011 (UTC)

The best exposition of what reversing the arrow of time would look like, IMHO, is the episode "Backwards" from Red Dwarf. --TammyMoet (talk) 16:16, 16 March 2011 (UTC)

That episode was completely unscientific (of course, it wasn't intended to be otherwise). They had people in the same universe with some remembering the past and some the future. That violates the 2nd law of thermodynamics. --Tango (talk) 17:02, 16 March 2011 (UTC)

Merlin in The Once and Future King lived backwards in time. He was getting younger as everyone else got older. 92.15.26.91 (talk) 20:53, 16 March 2011 (UTC)

Just to note...I watched this episode of the Wonders of the Universe series last night ('destiny') and I was not left in the slightest with the impression that nobody understood 'why' time went in one direction. There was a good 15-20 minutes dedicated to describing Entropy. (or have I misunderstood the question/show?) ny156uk (talk) 21:16, 16 March 2011 (UTC)

Energy Catalyzer

Is the Energy Catalyzer a hoax, or just bad science? 148.177.1.210 (talk) 13:23, 16 March 2011 (UTC)

If it was just bad science, the authors would at least try to get their work published in a real peer-reviewed journal. Instead, they created a blog entitled "Journal of Nuclear Physics" to seem like they're publishing their work in a reputable place. I'd call that behavior unethical and hoax-like. Nimur (talk) 13:53, 16 March 2011 (UTC)

Their patent application looks like it will fail because the inventors didn't adequately describe their device's construction, nor did they present appropriate evidence that it works as claimed: [9]. The difference between a 'hoax' and 'bad science' is, I would say, down to whether or not the inventors really believe their own claims. (A similar distinction exists at the fringe of the medical profession when one distinguishes a 'quack' from a 'fraud'.) TenOfAllTrades(talk) 15:12, 16 March 2011 (UTC)

How effectively can control rods stop fission?

It might be yet another question about the Japanese reactor malfunction, but I can't find any article which addresses this issue: as far as I know, if the control rods are fully inserted, they stop the reaction by capturing the neutrons which cause the fission. Weren't the control rods inserted in the case of the current accident? I assume they were, as most the news sources say the reactors were stopped at the first warning, before the quake hit. So, if the reaction is stopped, what causes the overheating? I know it might not be an instantaneous stopping of the fission, but what exactly is generating heat even after many days after the malfunction? I know the reactors are hot and don't cool themselves quickly, but something is generating heat, doesn't it? --87.169.20.137 (talk) 15:33, 16 March 2011 (UTC)

Yes, the reaction is stopped. (The residual neutrons that avoid the control rods are of little consequence for the total energy balance.) The problem is that nuclear reactor generated a lot of unstable radioactive isotopes during its run. It is the decay of these isotopes that generates the heat after the control rods are inserted. This heat is known as decay heat, and there is really nothing one can do to avoid it. All you can do is wait for the various fission fragments and such to decay to a more manageable level. Dragons flight (talk) 15:41, 16 March 2011 (UTC)

The heat is generated by spontaneous decays of the radioactive material. That is, a nucleus in an atom sends out a particle at high energy, which heats the surrounding material. This is as opposed to fission, where a neutron from outside hit and shatter a nucleus. As Dragons flight says, you just have to wait for this to cool down. Interestingly this means that the severity of the situation is slowly but steadily decreasing. This must feel like gratingly bad choreography for the news media, which wants the perceived risk to increase, so as to keep our attention. EverGreg (talk) 15:47, 16 March 2011 (UTC)

In Japan, with one new nuclear reactor exploding or burning down each day and increasing radiation levels and evacuations, the media are doing fine for stories. See also Timeline of the Fukushima nuclear accidents. The government coverups, company misdirections and simple lack of understanding at Chernobyl and 3 Mile Island provided plenty of news fodder as well. 75.41.110.200 (talk) 16:07, 16 March 2011 (UTC)

(ec) That is not the only source of heat - remember the rods are filled with uranium and, in one reactor, a bit of plutonium, that is constantly fissioning all on its own. The "chain reaction" is stopped by the control rods but natural radioactive decay will persist for thousands of years. 75.41.110.200 (talk) 16:02, 16 March 2011 (UTC)

Although it will only be acutely quite dangerous and hot (e.g. require being kept in a spent fuel pool) for a few decades. The heat is not caused by plutonium spontaneous fission (which is not that much), but all of the fission products that are in there. --Mr.98 (talk) 16:24, 16 March 2011 (UTC)

Even the MOX fuel reactor has only a couple percent plutonium; its almost all Uranium. 75.41.110.200 (talk) 16:37, 16 March 2011 (UTC)

I was under the impression you were referring to the plutonium content of the spent fuel. It is only 1% or so. The spent fuel is itself some 96% uranium. Most of the heat and immediate radioactivity, though, comes from that 3% or so of fission products, really nasty stuff that is very unstable. That's the stuff that mostly burns itself out after 20 years or so, leaving only the stuff that is radioactive in the very long term, but not as "hot". --Mr.98 (talk) 18:32, 16 March 2011 (UTC)

The danger of the current situation is not that they are unexpectedly hot, but that the reactor cores have at various times been exposed (without coolant). That allows the spent fuel in them (chock full of fission products) to get dangerously hot and dangerously radioactive. If it gets too hot and causes parts of the core to melt (the "meltdown") that can create new problems, e.g. spent fuel pooling on the bottom of the reactor vessel, which can create its own criticality problems. If there wasn't a coolant problem, the reactor would still be "hot" but not hot enough to cause any trouble. The problem is the coolant, not that the reactors are "out of control" in the chain reacting sense. --Mr.98 (talk) 16:27, 16 March 2011 (UTC)

"and dangerously radioactive" - exposed rods are not more radioactive. They may release more radiation or radioactive compounds in places where you don't want them but they don't increase in rate unless there is a criticality event. High temperatures, in fact, make criticality harder to achieve. See Critical mass#Changing the temperature 75.41.110.200 (talk) 16:37, 16 March 2011 (UTC)

Well, pedantically: the rods are dangerously radioactive as it is. The coolant water shields quite a lot of that. The removal of coolant means your radioactivity is going to be higher in places it wouldn't otherwise be. The relationship between temperature and criticality is not entirely germane here — it's not a question of trying to create a critical mass deliberately, but the mechanical action of melting the spent fuel or its containment. Which is bad for a number of reasons, criticality included. --Mr.98 (talk) 16:49, 16 March 2011 (UTC)

I don't think the difference is unimportant. The amount of misinformation increases with every news report - most of the "science experts" are getting things wrong as well. And I think you just agreed with everything I wrote. 75.41.110.200 (talk) 17:01, 16 March 2011 (UTC)

Yes, we agreed with each other. It was just clarification on both of our parts, in the end. :-) --Mr.98 (talk) 18:32, 16 March 2011 (UTC)

The possible melting of the fuel rods due to the secondary decays is sometimes referred to by china syndrome, but in that case Brazil syndrome might be a more appropriate moniker. Dauto (talk) 19:39, 16 March 2011 (UTC)

Well, the term China syndrome never did make much sense, given that it was implicitly meant to talk about reactors in the United States. No antipodal point of the United States is anywhere near China (easiest way to see this: Both the US and China are entirely in the Northern Hemisphere). If you take the United States and project it over to its antipodes, your projected image is mostly in the middle of the Indian Ocean.

(Does anyone know where this "straight through to China" meme originates?) --Trovatore (talk) 00:42, 18 March 2011 (UTC)

It's covered in the china syndrome article. --Tagishsimon (talk) 00:46, 18 March 2011 (UTC)

Well, not really. The article says that the name comes from the fictitious notion that "the other side of the world" is China. But my parenthetical question was where that notion (which is certainly much older) comes from.

It froze clean through to China

It froze to the stars above

At a thousand degrees below zero

It froze my logger love -- old song

--Trovatore (talk) 01:15, 18 March 2011 (UTC)

Strictly speaking, the melting of fuel is just a meltdown. The China syndrome is a specific subset of meltdowns where the material actually burns through the containment dome. --Mr.98 (talk) 21:38, 16 March 2011 (UTC)

Bird ID help...

So, my 4-year old asked for the name of a bird we saw today. We live in Raleigh, North Carolina. Sadly, I didn't get a picture, but I'll try to describe it the best I can. It was a passerine bird, shaped and sized like a Blue Jay, except it didn't have the tuft on top of its head, the head was perfectly round. The coloration was more like a Carolina Chickadee, i.e. all black and white and gray, but it wasn't shaped or sized like a chickadee, and it didn't have a chickadee's call. Two of them were fighting in my front yard, and they made sounds like a raspy back-of-the-throat sound, almost like the german or scottish 'ch' sound, but a longer in duration. If I can get a pic, I will take one and upload it, but right now does that sound familiar to anyone? To sum up, a bird roughly the same size and shape as a Blue Jay, with a round head, black and white coloration, which makes a distinctive "back-of-the-throat hiss" sound when agitated. Location: Raleigh, NC. Thanks to any help anyone can give... --Jayron32 17:57, 16 March 2011 (UTC)

Wild guess—do the pictures at Northern Mockingbird look anything like it? Deor (talk) 18:08, 16 March 2011 (UTC)

The shape is about right, but the neck on my bird was a bit longer, and the coloration is wrong. This one had more black around the head, and more sharply defined bands on the wing. Perhaps another kind of mockingbird? I'll follow that thread... Any other suggestions out there? --Jayron32 18:17, 16 March 2011 (UTC)

Magpies are corvid like blue jays, and have black and white markings. They tend to be a bit larger than jays, and are known to bicker and fight. (I'm not sure what species might be in the Carolinas at present) SemanticMantis (talk) 18:51, 16 March 2011 (UTC)

Yeah, I looked at Magpies, and that wasn't it either... Those have too much black, and the bill is too crow-like; these had a more jay-like or mockingbird-like bill. In fact, if the magpie fucked the mockingbird, you might imagine that offspring would look more like this bird. This one had a black stripe on the head, or maybe a black head, but the neck itself was more slender than the magpie, and the black did NOT extend to the neck. --Jayron32 19:32, 16 March 2011 (UTC)

Another clue: In my searches, the closest I can find (and it is pretty close in appearance) is the Gray Jay, which looked very much like my bird, but that bird doesn't have a range anywhere near North Carolina; and I have seen enough of these birds this year and in years past to indicate that this was not an accidental; these birds are common enough around here. So: does anyone have any clues on a bird which looks a lot like a Gray Jay but which lives in North Carolina at this time of year, and which makes the sound I noted above? --Jayron32 19:38, 16 March 2011 (UTC)

The problem is, you know what the critter looks like and we don't. Your mention of a "black stripe on the head" above made me think of the Loggerhead Shrike, but that's just another guess. We have a List of birds of North Carolina; you may want to peruse that. Deor (talk) 20:07, 16 March 2011 (UTC)

When you say that the colouration was like a chickadee, do you mean that it contained the same kind of colours or that the patterning was similar (i.e. with distinctive black cap and throat patch)? I'm going to chime with Hairy Woodpecker (and other woodpeckers) as something to check out, if only because it's technically not a perching bird and so might get overlooked, but is still shaped much like a passerine bird. Matt Deres (talk) 13:43, 17 March 2011 (UTC)

For another resource, whatbird.com has a great interface to its database, and an expert forum, so you might have better luck there. (can't link direct, it's on the spam list for some reason) SemanticMantis (talk) 13:54, 17 March 2011 (UTC)

Thanks for all your help guys! Unfortunately, my memory of the bird is fading, and all of these pics are starting to run together for me. Lesson learned: next time I'll get a pic. But I really do appreciate everyone that chimed in with suggestions! --Jayron32 18:18, 17 March 2011 (UTC)

Speed of WiFi

Would it be terribly incorrect to suggest that wireless signals — for cellphones, computers, what have you — travel through the air at roughly the speed of light? I know that this is not the speed of information transmission, and that I am speaking of the speed of light in atmosphere (not a vacuum). --Mr.98 (talk) 18:28, 16 March 2011 (UTC)

They travel through the air at exactly the speed of light in atmosphere, not just roughly. Note that while the signal travels at that speed, that isn't necessarily the speed at which information can be exchanged along WiFi signals; such information throughput is limited by things like bandwidth, both Bandwidth (computing) and Bandwidth (signal processing) are relevent to the idea. So, yes the speed at which the signal travels is exactly the speed of light, but the speed at which information can be exchanged between nodes in a network is significantly slower than that. --Jayron32 18:31, 16 March 2011 (UTC)

Thanks, that's what I thought, but I was afraid I might be being a dope if I were to say such a thing. --Mr.98 (talk) 18:33, 16 March 2011 (UTC)

You can't compare the speed of light (dimensions: distance/time) with the speed of information exchange (dimensions: bits/time). The time it takes for signals to travel from A to B affects the latency, not the throughput. Latency is, of course, caused by a lot of other things as well, which will usually have a greater impact - speed of light issues are relevant when you are going via a satellite, but that's about it. --Tango (talk) 18:36, 16 March 2011 (UTC)

Jayron, can you explain why the atmosphere has no effect on wave speed, as opposed to a tiny/negligible effect, as implied by Electromagnetic_radiation#Wave_model? — Preceding unsigned comment added by SemanticMantis (talk • contribs) 18:40, 16 March 2011 (UTC)

I assume by "They travel through the air at exactly the speed of light in atmosphere" he meant light and wireless signals go at the same speed in the atmosphere - but less that the "speed of light" (in a vacuum). Grandiose (me, talk, contribs) 18:43, 16 March 2011 (UTC)

Thanks, I will now read more carefully before posting follow-up questions :) SemanticMantis (talk) 18:54, 16 March 2011 (UTC)

(EC x 3) In short, no, that would not be terribly incorrect--Radio_waves says "Like all other electromagnetic waves, they travel at the speed of light." However, Electromagnetic_radiation#Wave_model says "speed of the wave (c in a vacuum, or less in other media)", which is an apparent contradiction. My understanding is that, in the atmosphere, EM waves 'effectively' propagate at the speed of light, but if you measure carefully, the speed is less, e.g. 0.999999999999999999999999c SemanticMantis (talk) 18:37, 16 March 2011 (UTC)

According to the 2nd paragraph of speed of light it's about 0.9997c. --Tango (talk) 18:50, 16 March 2011 (UTC)

I'm highly skeptical that radio waves travel at exactly the same speed as light in the atmosphere. That assumes that the atmosphere has the same refractive index for all wavelengths. Even over the visible spectrum, this is demonstrably false: we have rainbows. --99.237.234.245 (talk) 19:14, 16 March 2011 (UTC)

Radio waves are light. They are not visible light, but the sensitivity of the cells at the back of your retina to them doesn't make the light itself fundementally different. Yes, as you note, the speed of a light wave through a medium, like the air, is dependent on the wavelength of that light, it's why the different colors of the rainbow are split by a prism; as white light passes through the prism, the different wavelengths slow down to different rates of speed, which causes them to seperate out. However, such an effect is mathematically predictable; and if you know the refractive index of the medium and the wavelength of the light in question, you can calculate the actual speed of that specific wavelength. A discussion of how to do so is covered at Refractive_index#Speed_of_light. This calculation works whether you are doing it on light at 600 nanometers (yellow) or 125 millimeters (2.4 GHz WiFi). So, while the speed of the light waves carrying the Wifi signal do travel slower than, say, the speed of yellow light waves in the same atmosphere, the speed of the Wifi signal travels at exactly the same speed as all light waves of that frequency in that medium. So to answer the OP's question, pretty much exactly as I answered it, but with less ambiguity: The speed of the WiFi signal through the atmosphere is exactly the speed of that wavelength of light through the atmosphere. --Jayron32 19:28, 16 March 2011 (UTC)

No, Jayron. That effect cannot be mathematically calculated and the article you site describes un important relation which cannot by itself be used to predict the effect from first principles. A detailed model of how the electrons in the matter interact with the light must be used as well. Or it can be experimentally measured which is much easier. Dauto (talk) 22:41, 16 March 2011 (UTC)

OK, so that part's a bit wrong. But the radio portion of the light spectrum is still light and signals travel at the "speed of light" in whatever medium it is, regardless of what that speed is, and what complicated calculations or experiments you need to determine it. Our ability or inability to do the calculation doesn't change the fact that it is still 100% accurate to say that the WiFi signal, being itself light, will travel at the local speed of light, whatever it is... --Jayron32 15:39, 17 March 2011 (UTC)

Down here at sea level (and in fact, at all altitudes that humans normally go to), it's safe to say that radio frequencies, ranging from the low-frequencies (ULF, VLF, and so on, at 300 - 30 kHz), up to High Frequency (10 MHz) up to VHF, UHF, microwave, and so on, (essentially, all frequencies from ~ 300 Hz to 30 GHz) travel with the same speed in atmosphere. Their attenuations depend highly on frequency, but their speed in air is essentially the same as the speed in a vacuum (at least, let's say, to "several decimal places"). As has been pointed out, this is something like 0.9995 c (in other words, for many practical purposes, equal to the speed of light in a vacuum). This is mostly because at such long wavelengths, the wave "doesn't even see" the neutrally-charged atoms of the atmosphere. If you send the wave through non-atmospheric conditions, especially if there are free electrons and ions, (like when you're beaming signals through the ionosphere, about 100 kilometers above sea level), then you start getting neat frequency-dependent wave propagation speeds, because the air molecules interact with the radio signal. This causes the skywave effect, among numerous other electromagnetic phenomena.

Also, once you get past the millimeter-wave / micro-wave band, and start hitting long infrared and visible light, regular sea-level atmosphere does actually behave non-ideally. This is, of course, because the wavelength of infrared and visible light is very close to the scale-lengths for atmospheric molecule interactions. So, if you get to higher frequencies (like infrared, visible light, ultraviolet), then molecular interactions and scatterting cause frequency-dependent index of refraction. Hence, blue sky, red sunsets, seeing light bend over-the-horizon at dusk, and so on.

So - briefly summarized: in Earth atmosphere, all waves between ~300 Hz to 30 GHz travel at the same speed, which is very close to speed of light in a vacuum. In other conditions, or at other wavelengths, various non-trivial interactions cause frequency-dependent wave speed. Nimur (talk) 16:31, 17 March 2011 (UTC)

What substance has the highest known melting point?

What substance has the highest known melting point?

Our article Tantalum hafnium carbide stakes its claim, but its source is the Encyclopedia Britannica, and even the EB article only says it's "one of the most refractory" chemical compounds.

(I was looking this up out of curiosity because of the ongoing meltdown, of course, and then wanted to add a mention of the record-holder to our melting point article.) Comet Tuttle (talk) 18:45, 16 March 2011 (UTC)

Well, some substances can't assume a liquid state at any temperature, and even for those that can, the melting temperature is a function of pressure. Basically there are three ways for a solid to change state: (1) melting; (2) sublimation; (3) breakdown of internal structure. Since even atomic nuclei will break down at sufficiently high temperatures, I would guess that the substance at which a solid-to-liquid transition occurs at the highest temperature would be neutronium (at extremely high pressure). Looie496 (talk) 21:09, 16 March 2011 (UTC)

I'd throw in my vote for the ultra-high temperature ceramics, which are an entire class of materials. These include hafnium diboride, zirconium diboride, and some similar materials. These materials usually ablate before melting; their phase transition characteristics are complex (sort of entering a "glassy" amorphous phase which might be considered fluid-like). Here's a NASA report on their material properties - they sort of "melt" (braze) in contact with certain metallic lattice faces, but never actually "liquify." Nimur (talk) 21:18, 16 March 2011 (UTC)

I'm not sure it's really meaningful to talk about neutronium as being a solid; our article on degenerate matter describes it as a degenerate neutron gas, but 'fluid' might be suitable as well. TenOfAllTrades(talk) 00:14, 17 March 2011 (UTC)

Sorry, I should have clarified that I was curious about materials' melting points under "normal" conditions, say, at 1 atm. Comet Tuttle (talk) 06:01, 17 March 2011 (UTC)

Maybe what you really want is the substance that remains solid and holds its strength through the highest temperature, at one atmosphere. That gets around all the quibbling about things that sublime or decompose rather than melting. --Trovatore (talk) 06:13, 17 March 2011 (UTC)

When evaluating materials also pay attention to what happens to them under neutron bombardment. Ideally you want to use elements that can't become radioactive for long (so zirconium is out). You also want materials that don't become too weak (or that can be annealed easily). Ariel. (talk) 09:11, 17 March 2011 (UTC)

Tungsten and Platinum have long been valued as non-exotic and non-theoretical metals with fairly high melting points. Edison (talk) 05:14, 18 March 2011 (UTC)

Where are the robots?

Japan appears to be the world leader in robot technology. So why arent remote-controlled robot things being sent in to fix the nuclear reactors? 92.15.26.91 (talk) 21:50, 16 March 2011 (UTC)

Because robots take a while to be planned and built. And I don't think it's quite as easy as just sending a robot in and fixing it. --T H F S W (T · C · E) 21:54, 16 March 2011 (UTC)

You're right it wouldn't fix the problem but I guess robot/s may be helpful to continue to try and cool the reactor when there are temporary radiation spikes which require the removal of workers if they had them (which they don't). Just don't use ones with most types of lithium ions batteries... Nil Einne (talk) 22:07, 16 March 2011 (UTC)

You'd think at least we could have some of those bomb robots from Iraq in there, just keeping an eye on the fires. Wnt (talk) 00:10, 17 March 2011 (UTC)

Rest assured, the robots are being put to work in disaster recovery any way they can. See e.g. this blurb from IEEE Spectrum: [10]. SemanticMantis (talk) 00:09, 17 March 2011 (UTC)

But as far as the reactors are concerned, Asimo Asimov taught us that positronic brains are even more susceptible to damage from sufficiently intense gamma radiation than humans are. -- 110.49.241.128 (talk) 00:55, 17 March 2011 (UTC)

Robots tend to have to be designed for a specific purpose. I guess no-one anticipated the current problems or thought them likely enough to design robots to deal with them. --Tango (talk) 01:10, 17 March 2011 (UTC)

I certainly hope they do after this incident. ScienceApe (talk) 03:21, 17 March 2011 (UTC)

One thing worth noting about robots: even if we have exactly the prototype to churn out, having complex self-powered joints move around substantial amounts is extremely sensitive and prone to breakdown. The director of Death and the Powers gave a seminar here and noted, when asked if robots would take over the world, that he'd be happy if he'd have one week when a robot didn't break down on stage. SamuelRiv (talk) 04:37, 17 March 2011 (UTC)

Nuclear power is no more dangerous today than it was two weeks ago. If it wasn't worth it to develop such robots two weeks ago, it isn't worth it today. --Tango (talk) 22:21, 17 March 2011 (UTC)

Would you like to be at a nuclear plant that might meltdown and is leaking dangerous radioactive material into the environment? If you would, I'm sure Japan would love to have your assistance at Fukushima to help prevent a catastrophe. Personally I think investing in robots that can handle dangerous work like this is worth it. ScienceApe (talk) 22:38, 17 March 2011 (UTC)

Its a pity that no-one appears to have a remote control device that you can just clip into a standard vechicle such as a bulldozer or tractor, or even a tank or riot-control water-cannon wagon, in place of the driver. Even something crawling along at 1mph would be very useful. Wouldnt a tank offer the crew protection against radiation? 92.24.180.239 (talk) 15:15, 17 March 2011 (UTC)

Well steel is better then nothing, and I suppose you could always upgrade it with some lead additions, but after a while, you have a radioactive tank that you need to stash somewhere away from people, but I am not really sure what a couple people in a tank are going to be able to help anything without leaving the tank. Unless it is like a bulldozer engineering unit tank. Googlemeister (talk) 19:04, 17 March 2011 (UTC)

BoingBoing covered this very issue today. Main conclusion: "robots and power plants have to be designed with each other in mind. Fukushima Daiichi, which dates to the 1970s, may simply not be navigable to newer nuclear helper 'bots." --Tagishsimon (talk) 22:24, 17 March 2011 (UTC)

There should be proper robots built for the purpose but they will need very good protection from radiation. As far as I know any electronics they tried to use at Chernobyl failed very quickly indeed in the order of minutes. It's quite horrifying that they used humans for instance to look at things where video cameras wouldn't work. Dmcq (talk) 23:56, 17 March 2011 (UTC)

It was apparently cheaper for the Japanese power company involved to do little in regard to providing remote operated equipment, in favor of letting workers injure their health by large radiation exposure. For instance: a boom truck, remotely operated, could have used a demolition tool to cut a hole in the masonry panels surrounding the top of the reactors. This would have allowed air circulation and prevented the hydrogen explosions that demolished the tops of the buildings. Then, guided by a TV camera, a water spray could have been used to refill spent fuel pools thought to have little or no water. Instead, there was a silly attempt to use helicopters to drop seawater on the roofs of the buildings, with only a tiny fraction even hitting the roofs, with radiation exposure to the flight crews such that the efforts were suspended. Then police "antiriot water cannons" were used to spray water in the general direction of the buildings, but the radiation levels were too high to get very close for very long, and it did little good. (Does Japan have lots of riots where water cannons are needed, like Soviet satellite states used to?) It all evokes images of trying to fix an overheated car radiator by throwing a bucket of water at the car, with the hood only slightly ajar. There are bomb disposal robots and firefighting robots aplenty, with remote control and remote TV viewing. If a wall panel were removed, such a tracked device could have been inserted via a boom truck. We have had remote operated devices on Mars for years, for pity's sake, going around and sending back 3D color pictures, and cutting into things. We have seen teleoperated submersibles in the Titanic. There are even teleoperated robotic soldiers, which can shoot at the enemy or retrieve wounded soldiers. We have had the Darpa Challenge, with true autonomous robotic vehicles driving all over a town, obeying traffic signals, and in and out of parking garages. Google has operated autonomus cars for over 100,000 miles on California highways. The Space Station has teleoperated devices to assist the astronauts, with the ultimate aim of maintaining the station when no humans are on board.How much easier where all that is needed are teleoperated devices to send back pictures and thermal images, and aim hoses. How much progress has the nuke industry demonstrated since the post-Three Mile Island robotics developments? Why must they call on humans to "make the supreme sacrifice" rather than showing some initiative in developing and applying robotics and remote operated devices? Yeah, Japan has lots of cute little Asimo robots which dance around, but no apparent development and deployment of anything useful in a situation like the Fukushima 1 mess. A remote operated crane and a remote operated cutting torch on a boom truck could clear away the twisted structural steel overlaying one of the reactors after the hydrogen explosion, so that the concrete of the containment would be exposed, allowing better viewing and access to the spent fuel pool. Edison (talk) 04:56, 18 March 2011 (UTC)

After an inexplicable one week delay, the Japanese authorities have requested robots from the Massachusetts company iRobot, which can travel around in the reactor to measure radiation and to pull hoses where water is needed. Great idea, if only they had done it on day 1, or if they had been proactive and had some in-country as a precaution against a blackout at a nuke plant. Edison (talk) 19:53, 19 March 2011 (UTC)

I didn't see anything about the electronics working in an environment like that and to me they don't look heavy enough to be radiation hardened either. I expect they've looked into that but if not they very likely will die in no time flat. Dmcq (talk) 00:02, 20 March 2011 (UTC)

This is a question of interest. The 4000 millisievert/hour level may not be all that high a radiation level for the military grade electronics, although a 15 minute exposure would cause radiation sickness in a human. Radiation level sensing is one of the regular functions, via the "CHARS" package, so some degree of survival in a high radiation zone would be expected. I expect robots could be used in zones where humans would not be sent, even if the robots cannot survive the highest imaginable radiation levels. It would be easy enough for the makers or the military to test. The high temperatures might be a problem, since the Warrior has a 104F (40C) operating high temp limit. Its electronics are hardened to Mil Std-461 and MIL-Std-464 Do those specs give a radiation limit? All I see is discussion of electromagnetic radiation, not ionizing radiation. The article Radiation hardening mentions 5000 Rads as a dose which would disable regular commercial silicon chips. The 4000 millisievert/hour highest dose reported would take 12 hours of exposure to deliver that dose, if the chip were totally unshielded and not rad hardened. Radiation hardened chips are available, and the electronics could be shielded. Low-power Schottky chips can stand 1,000,000 Rad, per the article, which would give a human a lethal dose in 2 seconds. Edison (talk) 01:58, 20 March 2011 (UTC)

March 17

How often does Sansevieria trifasciata bloom?

How often does Sansevieria trifasciata (snake plant) bloom? My mother has one that is blooming now and she says that it is rare. Bubba73 ^{You talkin' to me?} 01:04, 17 March 2011 (UTC)

When grown as a houseplant, the period between blooms is highly variable, based on sun exposure, and how root-bound it is in its container. I'm sure you could not see a bloom for several years in some cases, especially if starting from a small clone in a large pot. Under 'average' houseplant conditions for a mature individual, expect a bloom every 2-4 years. They are more likely to bloom the more root-bound they are, because this is when they have reached the limit of vegetative growth. Note that it spreads rapidly through clonal growth in its natural environment, so sexual reproduction every year is not critical for long-term population success. Also, as a side note they have nectaries on the base of each flower on the raceme, which each produce a large drop of sweet nectar. Your mother may enjoy trying some; it tastes much like honey :) SemanticMantis (talk) 02:32, 17 March 2011 (UTC)

This one is in a small pot but it gets plenty of sunlight (next to a picture window). Mother says that she has never seen one bloom. She had me take photos to show the women in the beauty shop to prove that it does bloom. Bubba73 ^{You talkin' to me?} 02:58, 17 March 2011 (UTC)

I should have flagged (OR) above, maybe 2-4 years is a bit optimistic, as it is in the same family as the century plant, which is known for its long bloom interval. The bloom definitely feels special when it happens. SemanticMantis (talk) 14:00, 17 March 2011 (UTC)

That helps explain it, thanks. Bubba73 ^{You talkin' to me?} 15:37, 17 March 2011 (UTC)

Scent

I'm a hunter and I know how good an animals sense of smell is. My question is, all else considered, does hair make it easier for an animal to smell you? I heard it helps to vaporize it, which sounds bad, as that odor no doubt travels.

Any help would be appreciated, and if you know of any odor blockers (not stuff that leaves you smelling like perfume, but true blockers) I'd be much obliged. —Preceding unsigned comment added by 148.61.220.214 (talk) 01:08, 17 March 2011 (UTC)

Body odour is increased by the presence of pubic hair. That has even been proposed as the reason we have pubic hair. --Tango (talk) 01:24, 17 March 2011 (UTC)

Maybe for our naked cave-dwelling fore-bearers, but wouldn't the clothing of a hairless human absorb and hold odors just as well as, if not better than, body hair?

I assume he's not talking about shaving his body and then going out into the woods nude. APL (talk) 02:11, 17 March 2011 (UTC)

Here's a blog called ArcheryTalk that discusses this issue from a bowhunter's perspective. The author discusses five main strategies in further detail there:

1. Cleanse – Your body……..
2. Neutralize – Odor causing Bacteria…….
3. Maintain – Clean clothing/footwear…….
4. Mask – We’ll talk about this one……
5. Play the wind – Enough said………

He "neutralizes" by scrubbing down with an antiseptic like Betadine, and claims that a product called 'Bob’s “Skunk Essence”' works as an effective mask for him.

Also, as far as hair-odor-blockers, here's a plug for the product Invisible Hunter Shampoo^tm:

"Sometimes overlooked, human hair carries odors from not only one’s own body but from other environments that one has visited. A good practice of shampooing with Invisible Hunter’s Scent–Removing Shampoo is all you need to eliminate dirt and odors. Invisible Hunter’s Scent-Removing Shampoo will leave your hair clean and soft while providing you the extra scent control the serious hunter seeks."

WikiDao ☯ 04:20, 17 March 2011 (UTC)

Just curious, how do you get rid of the skunk essence smell. Great in the woods, real bad at home! Richard Avery (talk) 12:00, 17 March 2011 (UTC)

Real hard-core hunters wouldn't care about that. Real hard-core hunters are also probably single. (If not, see No true Scotsman) :-) . {The poster previously known as 87.81.230.195} 90.197.66.165 (talk) 01:48, 18 March 2011 (UTC)

Thanks, all. I like your comment though that clothes themselves would be a big issue...Do you know some products specific to cleaning your clothes, but not leaving it smelling like Tide, either? Thanks again. —Preceding unsigned comment added by 148.61.220.214 (talk) 03:25, 18 March 2011 (UTC)

More examples of millisievert doses?

I am skeptical of Sievert#Yearly_Dose_Examples-- for example, how could "some parts of Iran" naturally have half the carcinogenic dose? Can anyone find a good source for this kind of information? Shii (tock) 01:10, 17 March 2011 (UTC)

What you are calling the "carcinogenic dose" is the dose at which the probability of you getting cancer is measurably higher than normal. It isn't much higher, though. It is still an insignificant dose as far as individuals are concerned (other factors, such as diet and lifestyle, affecting cancer cause far more variation from person to person). When you look at a large number of people, it becomes significant, but only just. --Tango (talk) 01:21, 17 March 2011 (UTC)

Seems reasonable to me. Why do you find that so surprising? Dauto (talk) 03:01, 17 March 2011 (UTC)

The figure "Background radiation in parts of Iran, India and Europe: 50 mSv/year" sounds somewhat high to me, even though it comes from a BBC source - a value that high must be very localised. Our article on Ramsar, Mazandaran says "Some areas around Ramsar have the highest level of natural radioactivity in the world, due to the presence of radioactive hot springs ... the medium value in the Ramsar area is 10.2 mSv/year" - although background radiation levels in and around the springs themselves can be much higher. Gandalf61 (talk) 07:12, 17 March 2011 (UTC)

Full meltdown?

According to this, http://www.cnn.com/interactive/2011/03/world/interactive.nuclear.japan/index.html?hpt=C2

Three mile island and Chernobyl were only partial meltdowns. What's a full meltdown? This never happened? I always thought Chernobyl was a full meltdown. How far deep can a meltdown melt through stuff? ScienceApe (talk) 02:50, 17 March 2011 (UTC)

Nuclear meltdown refers to the heating of the Nuclear reactor core to the point where it melts; i.e. turns to a liquid. In a partial meltdown, parts of the core would melt, and other parts would remain intact. In a total meltdown, the entire core would be a pool of liquid at the bottom of the reactor; AFAIK this has never yet happened. In Chernobyl, the problem wasn't no much a meltdown, which is a serious but managable event, it was the excursion (i.e. the fissile material reached criticality) which damaged the containment security in the plant and allowed radioactive material to be sent into the atmosphere. Indeed, our article on the Chernobyl disaster doesn't even mention a meltdown, except briefly in passing. Indeed, an excursion (basically the reactor turns into a bomb) is a far more serious event than a meltdown; once the reactor core exploded, whether or not it melted is somewhat moot. --Jayron32 03:01, 17 March 2011 (UTC)

Side-questions: I'm kind of kidnapping this question, but the questions about nuclear reactors are a hot (sorry for the pun) topic this week. So, here for the questions: (1) if we let it meltdown, wouldn't this bore a hole and let the atomic material slip through this hole, and in the same process, cover it with other molten substances? Sounds pretty optimistic, I know. (2) Have anyone let a small core meltdown to test the question (1)? (worse experiments indeed happened) Quest09 (talk) 18:15, 17 March 2011 (UTC)

1. Probably not. I mean if you put a pile of melted nuclear fuel it might burn down into the earth, but unless the nuclear pile is actually vaporizing everything it touches, how is the dirt and rocks and such going to get out of the hole? Plus all the stuff you are melting is becoming radioactive at the same time. 2. I would really, really hope not. That sounds like a very expensive experiment with potential to cause enormous environmental damage and large negative impacts to human health and for what real purpose? Googlemeister (talk) 19:00, 17 March 2011 (UTC)

See corium. Once the fuel melts, you get a radioactive slag of fuel oxides plus everything else the fuel encounters. If the molten corium encounters water (say, the suppression tank underneath the reactor) you get a steam explosion that spreads a radioactive dust over a huge area. --Carnildo (talk) 23:29, 17 March 2011 (UTC)

Earths axis

Does the 6.5 inch shift in the earths axis from the earthquake create any changes, such as change in seasonal patterns or tides? —Preceding unsigned comment added by 68.36.96.146 (talk) 03:02, 17 March 2011 (UTC)

The circumference of the earth is roughly 40,000,000 meters. 6.5 inches is .1651 meters. .1651/40,000,000 = 0.0000000041275 or 4 parts per billion variation. That's pretty imperceptible. --Jayron32 03:08, 17 March 2011 (UTC)

In a related note, I've been trying to find out which way it's shifted. Here in Connecticut, am I closer or farther from equator? APL (talk) 07:36, 17 March 2011 (UTC)

It means Mrs. Claus is yelling at Santa to get his fat ass off that Nintendo game and go out there and move that pole! Wnt (talk) 17:14, 17 March 2011 (UTC)

Jayron, thanks for enlightening us on the imperceptibility of 6.5 in. in relation to the circumference of the earth. Does someone else care to answer the straightforward question? it obviously is different that before, so what does that difference equate to in more or less sunlight each day for the northern hemisphere? —Preceding unsigned comment added by 165.212.189.187 (talk) 17:28, 17 March 2011 (UTC)

The Earth's axis already shifts seasonally (at a greater magnitude than caused by the Earthquake, I believe), due to the rearrangement of mass caused by the weather (mostly the redistribution of water, I believe). Here are a couple articles on it, though they relate more to the change in day length than the axis shift [11], [12]. As these articles point out, pretty much every earthquake redistributes the mass at least some, but you can also see that the changes are on par with the yearly variation that is experienced anyway, regardless of earthquakes. The answer is definitely "no", this Earthquake will not have a noticable effect on seasonal patterns or tides. Buddy431 (talk) 18:03, 17 March 2011 (UTC)

Addendum: Here's a source that explicitly addresses the axis shift issue: the Earth's axis shifts about 3.3 ft seasonally, about 6 times the shift caused by the quake. Richard Gross, a Geophysicist, says "These changes in Earth's rotation are perfectly natural and happen all the time. People shouldn't worry about them." [13] Straight from the mouth of a real scientist. Buddy431 (talk) 18:07, 17 March 2011 (UTC)

This shift is in addition to the regular shift of the seasons. Who said anything about worrying, what did he say about curiosity, that it killed the cat? That is why this desk exists - to inform and enlighten not easy worrys of. —Preceding unsigned comment added by 165.212.189.187 (talk) 18:24, 17 March 2011 (UTC)

And it's doing a great job - who knew that the Earth's axis moves? Or that there was both an axis and a figure axis to keep track of? Wnt (talk) 23:32, 17 March 2011 (UTC)

Storing electricity via “counterbalance” batteries?

Some time ago, I asked about the viability of using dams to augment sporadic electricity production via windmills and solar panels. The method is used in Sydney. When more than enough power is being produced, the power not needed is used to raise water to storage dams, where it can later be used to create hydroelectric power. This is, in effect, a battery, and I was surprised that it returned about 70% of the power it took to raise the water. Now, there are other ideas for batteries, as not all that many sites have big dams nearby.

My idea is: when the wind is strong and more power than is needed is being produced, why not have the mill raise a heavy weight chained below the vanes? When power is needed later, the weight can be slowly lowered, turning the vanes via gears and generating electricity.

I did read in New Scientist, years ago, in one of their historical featurettes, that in the early 20th Century, there were at least some English farmhouses which had a wind mill such as I have described on their thatched roofs. When the vanes turned, they could raise a weight, enclosed by a cylindrical cage located in the main room. When the wind died down, that weight could be allowed to slowly descend, generating electricity. I can’t find that source now, and I am wondering if someone knows anything about such an ingenious contraption. Myles325a (talk) 03:57, 17 March 2011 (UTC)

The idea's good - but the "engineering details" are hard. Gravitational potential energy is usually approximated as mgh - so pick some reasonable numbers for a mass (let's say, 10 tons), and a tower height (say, 100 meters); how much energy is that going to actually store? About ten megajoules of gravitational potential energy - about 3 kilowatt-hours. And that's a huge weight, and a really tall tower! Now, consider that one single barrel of oil contains (in the form of chemical energy) about one-thousand times as much energy as our massive 10,000kg, 100-meter-tall contraption!

To store a lot of energy in the form of gravitational potential energy, you need a lot of mass - which is why pumped storage hydroelectric is the only practical way to do it. Nimur (talk) 04:29, 17 March 2011 (UTC)

Myles325a's suggestion was used in practice for a couple of centuries in the longcase clock. I agree with Nimur that the attraction of using water is that vast amounts of it are available, and can be pumped into elevated storage. Solid components that could be used for storage of energy are miniscule compared with the mass that is available as water. Dolphin (t) 04:34, 17 March 2011 (UTC)

The use of such dams is not fondly regarded by environmentalists. Realize that such a system creates a large body of water without a shoreline, but just a large muck zone that is irregularly covered by water. Wnt (talk) 04:51, 17 March 2011 (UTC)

A similar system installed on a tidal shoreline can be more than 100% efficient (in effect) if the seawater is pumped up at high tide and used to generate electricity at low tide. On a coast with a big variation in times of high tide (such as the UK) such a system would be economically beneficial, though environmentalists would not be happy (but very few people are happy to have any generation scheme in their back yard!) Dbfirs 13:46, 19 March 2011 (UTC)

Grid energy storage covers almost all options for power storage. Instead of raising a weight with a windmill, pumped storage (already mentioned) and flywheel storage seem more viable. Zunaid 13:18, 21 March 2011 (UTC)

What exactly is the reason for the radioactivity?

I'm a little confused after having read Fukushima I nuclear accidents. If the containment vessels are indeed all intact, what exactly is the source of the radiation that has been detected? Is the problem that water within the containment vessel is being made radioactive as it flashes into steam and gets vented (as an emergency measure) because the pressure within the containment vessel is high enough? Wouldn't this mean the vented steam is riddled with decay products? I'm not very clear on whether this reactor design has water pumped directly at the fuel rods so there's essentially direct contact between the fuel rods and the water that gets flashed into steam and then spins the turbines. On reflection, I suppose it must. Doesn't this mean that these "containment vessels" aren't actually able to be sealed? Comet Tuttle (talk) 06:26, 17 March 2011 (UTC)

The main thing is that spent nuclear fuel is kept in open ponds with very little containment. That's where most of the radiation has come from - there's a lot more to be released from there than from the reactors themselves. This is mostly slovenliness - there are other countries which have moved largely to dry cask storage. It is well known that in any natural disaster (such as a major pestilence or all-out civil war) anywhere in the world, which would cause nuclear reactors to go unattended, eventually the reactor will shut down, the diesel backup will run out, and the spent fuel pools will go Chernobyl at every unattended site. In addition, the containment for #2 is cracked.^[14] Wnt (talk) 06:46, 17 March 2011 (UTC)

I only know of the Pebel bed reactors not using Spent fuel pools for the first few months or years. The heat generated for the first few half lives of the fast decaying isotopes is in an order of magnitude that all other methods are impractical. Most reactors store the spent fuel close to the reactor, this might change after the disaster.--Stone (talk) 07:22, 17 March 2011 (UTC)

I don't think it is "slovenliness" that dictates whether one uses wet storage. For one thing, Japan reprocesses — that usually dictates against dry storage. In any case, you need to store it in wet storage for awhile (at least a year) before you do anything else with it, so the really nasty stuff burns itself out. It's unclear to me how "old" the fuel in the wet storage is (you could calculate it if you knew the time between refuelings and the amount of spent fuel in there). --Mr.98 (talk) 15:01, 17 March 2011 (UTC)

Would someone more reliable than Wnt on physics-related subjects please confirm or deny what (s)he wrote above? Especially the claim that active cooling is the only defense against a Chernobyl-like disaster at any nuclear plant with a spent fuel pool? The article seems to say that this is false, but I don't know what to believe any more. -- BenRG (talk) 08:20, 17 March 2011 (UTC)

Yah I don't think he's right about that. Even if you left the reactor completely alone it wouldn't go Chernobyl. Especially once the control rods are in place a real catastrophe is pretty much impossible - and those rods are designed to fall into place at any disruption. It may melt down, but it will stay inside the containment. And the urnanium in storage can't go Chernobyl either. However it does seem that the containment pools are a weak spot. People paid a ton of attention to reactor design, and it looks like their designs worked. However the pools did not receive as much attention and most of the current problems (fires) are from those. Spent fuel pool#Status implies that someone noticed the problems and new designs are better. I have to assume that the Japanese fuel is not designed this way. Ariel. (talk) 09:03, 17 March 2011 (UTC)

To clarify, I used "go Chernobyl" to mean "produce all kinds of radioactive smoke and fire", not "break the reactor containment". I thought I was being clear there that the radiation would be coming from the pools. Wnt (talk) 10:34, 17 March 2011 (UTC)

Fukushima I nuclear accidents says:

"The nuclear fuel requires 1–3 years of constant active cooling (by flowing water) before the decay heat production gets low enough that effective passive cooling becomes sufficient to avoid excessive heating up to temperatures where the integrity of the fuel is at risk."

"At the time of the earthquake unit 4 had been shut down for maintenance and refueling since 30 November 2010. All fuel rods had been transferred in December 2010 from the reactor to the spent fuel pool on the top floor of the reactor building where they were held in racks containing boron to damp down any nuclear reaction. These recently active fuel rods were hotter and required more cooling than the spent fuel in units 5 and 6."

and mentions speculation "that the Fukushima management could have been engaged in an unsafe industry practice of re-racking spent rods in the pool well beyond its rated capacity, in effect heightening danger of melting and pool boil-off". Gandalf61 (talk) 09:51, 17 March 2011 (UTC)

So, the with problem with the spent fuel pools is that they are not contained . Also the fuel rods are still relatively rich in fissionable fuel and the racks that should hold them upright and provide some necessary separation to prevent criticality coming about, have been subjected to several server shakeings. If some off these racks (and any other safety devices like boron separation sheets) have been badly damaged or collapsed by the quake, then the evacuation of the local population seem like a very sensible step to take. The fuel may not be combustible but it can possible go critical again, given the right circumstances and until they can dump a lot of boric acid into the pool, there may still be enough water to facilitate this.--Aspro (talk) 10:13, 17 March 2011 (UTC)

I suspect, but do not know for sure, that criticality is not the major concern with the spent fuel at this point. I suspect that they would need to really be in a very poor state (e.g. melted sludge) for that to be an issue. The bigger problem is that they are very hot and full of very nasty things, and could catch fire, vent, melt, etc. --Mr.98 (talk) 15:31, 17 March 2011 (UTC)

Radiation is still being released by the venting of steam from reactors 1 and 3 (and 2 which may not even be contained). This radioactivity was observed before any issues arose with the spent fuel pools at 3 and 4. However, this radioactivity was a lower level (didn't require removing plant workers) and was blowing out to sea at that time. 75.41.110.200 (talk) 14:42, 17 March 2011 (UTC)

Thank you all for your responses. A followup question: Is it known whether the spent fuel at the site is recently spent fuel, or has some of it been sitting there in a swimming pool for a couple of decades? Mr.98 mentioned that Japan reprocesses their fuel, so it sounds like it's probably recent; but do we have an article on the lifecycle of fuel uranium and plutonium in Japan? Comet Tuttle (talk) 16:25, 17 March 2011 (UTC)

I doubt we have an article on it. It should be information that is "out there" though — it's the kind of thing the IAEA would know definitely. My mangled German + Google Translate of this article seems to indicate that there are 50, 81, and 88 tons of fuel rods in the three pools, but that this is not their full capacity, and in fact they are relatively empty. (By comparison, the spent fuel at some US reactors is around ten times that amount — because we don't reprocess, and we don't have any long-term waste disposal options worked out.) This suggests to me that they are pretty recent, but I'm not sure. --Mr.98 (talk) 17:31, 17 March 2011 (UTC)

The most resent rods were removed in November and December. These two pages out line the problems. Danger of Spent Fuel Outweighs Reactor Threat . I guestimate that a 13 foot long rod must weigh about 5 or 6 2½ to 5 hundredweight. Zirconium alloy is a wondrous material and hopefully it will resist the contents of the rods or the pellets themselves from forming a 'pile' on the floor. If not, then it wont just be the cherry bosoms glowing in the sunset this spring and Japan will be off my itinerary for the foreseeable future. Came across this handy little chart showing the current state of play at a glance. Status of nuclear power plants in Fukushima as of 16:00 March 17--Aspro (talk) 18:18, 17 March 2011 (UTC)

I don't think you need to be flip about the risks (cherry "bosoms" and etc.) — there are real people's lives here at stake. We are not quite in the "joke about it" stage yet. --Mr.98 (talk) 19:59, 17 March 2011 (UTC)

And if I had worded the possible out come more accurately would you have then accused me of over exaggeration and scaremongering? --Aspro (talk) 21:09, 17 March 2011 (UTC)

In fact, no. I think your comment was in extremely bad taste. That's a different category from whether I think it was accurate or not. --Mr.98 (talk) 21:34, 17 March 2011 (UTC)

DANGER WILL ROBINSON! DANGER! DANGER! The THOUGHT POLICE are EVERYWHERE!! (and Mr.98 ALWAYS has to have the last word) I personally am looking forward to those delicious sushi legs and BBQ frogs wings! YUM220.233.166.18 (talk) 07:16, 1 April 2011 (UTC)

Iodized salt instead of iodide tablets

I have seen recent news stories about paranoid people hoarding potassium iodide tablets. I know that iodized salt is widely used for cooking, and contains either potassium iodide or sodium iodide (the two shouldn't really matter, right, since they all just disassociate to iodide ions in solution), couldn't one achieve the same effect by eating a lot of iodized salt? Or is there insufficient quantity of iodide in iodized salt? --98.210.210.193 (talk) 06:55, 17 March 2011 (UTC)

Right! My salt contains 0.0025% of potassium iodate. 1g would than be 2.5mg. Somebody said that a dose can be above 100mg of potassium iodate. This would be 40g of table salt. This is a deadly dose of salt for children and very unpleasant for adults. --Stone (talk) 07:33, 17 March 2011 (UTC)

The concentration apparently varies in iodized salt in important ways. I just read that Switzerland raised its concentration to 20 mg/kg from 15 mg/kg - your container appears to be just 15 mg/kg. Fortunately the article Thyrosafe I started is still knocking around, despite being deleted last December :( :), so I can see that the tablets are 130 mg for adults or 65 mg for children. So a child's dose of iodized salt required would be just, 8.6 kg?! Hmmm, I think you missed the % up there when you did the math before, unless I just fouled up.

Right! I missed the %. --Stone (talk) 13:52, 17 March 2011 (UTC)

Ooops, I messed up myself - the pills are labeled for 130 mg of KI, not 130 mg iodine, so it's only equivalent to 6.6 kg of iodized salt. If you pace yourself.... ;) Wnt (talk) 16:00, 17 March 2011 (UTC)

Anyway, since it's not needed in the U.S. where the crazy rush is, tossing a pinch of iodized salt over your shoulder would do no harm. And maybe that 8.6 kilogram figure will make people think twice about hammering their poor thyroids with that kind of iodine for no reason. Wnt (talk) 07:44, 17 March 2011 (UTC)

Can we react Tincture of iodine with something commonly available (baking soda?) to make sodium or potassium iodide? Ariel. (talk) 09:17, 17 March 2011 (UTC)

Just don't react it with ammonia or you'd get a pill with a kick to it. No, scratch that, I would say don't try this at all! Who knows what kind of impurities you'd choke down, not the least of which being iodine itself. But as you know, I'm not giving medical advice here. Wnt (talk) 10:30, 17 March 2011 (UTC)

"Japan radiation fears spark panic salt buying in China" -- Finlay McWalter ☻ Talk 15:08, 17 March 2011 (UTC)

Would eating some tinned fish or other seafood be of any use in an emergency situation? (Seafood - contains iodine). 2.97.215.199 (talk) 23:42, 17 March 2011 (UTC)

Well, for edible seaweeds e.g. kelp: "12 different species of seaweeds were analyzed for iodine content, and found to range from 16 microg/g (+/-2) in nori (Porphyra tenera) to over 8165 +/- 373 microg/g in one sample of processed kelp granules (a salt substitute) made from Laminaria digitata.";^[15] "Edible seaweed contained I levels of between 4300 and 2,660,000 micrograms/kg";^[16] (summarizing these two) "the average iodine content of kelp of 1,500 to 2,500 μg/g".^[17] So we're looking at roughly 2 mg of iodine per gram of kelp (I assume these are all dry weight), if you happen to get an average sample, with a just ridiculous amount of variation. So eating 65 grams, a plausible dose, would be equivalent to the 130 mg tablet - though you might end up getting four times as much if you are unlucky. Or you might get less than a mg. Wnt (talk) 02:38, 18 March 2011 (UTC)

My ex (who is a third year undergraduate) has made over $1000 selling KI on eBay... John Riemann Soong (talk) 18:48, 19 March 2011 (UTC)

Why does the World suffer from nuclear phobia?

Ever since Chernobyl, people have had a strong irrational fear of nuclear power. The public prefers coal fired power plants over modern ultrasafe nuclear powerplants, even though the dangers of global warming are far, far worse than that of a Chernobyl-type disaster. People are now fleeing Tokyo in airplanes, when merely being aboard the airplane at 40,000 feet altitude will expose people to 100 times more radiation than they would get if they were to stay in Tokyo. How can we explain this irrational behavior? Count Iblis (talk) 16:45, 17 March 2011 (UTC)

Just because the reading on a Geiger counter is the same doesn't mean the exposure is the same. In an airplane, you get off and the exposure ends. But in Tokyo the counter would be clicking due to various isotopes in the air, water, environmental surfaces which you might inhale or ingest and become exposed to for years to come.

Still, I think it is reasonable to assume many of the people fleeing are convinced that the radioactivity will become much worse, or that basic necessities will become even harder to find than they are now. After all, many people would have left the tsunami-disrupted country even without a nuclear situation. Wnt (talk) 16:52, 17 March 2011 (UTC)

Your premise is that people's fear of the ongoing nuclear crisis is irrational, but you would have to cite a source for that. What makes you think it is irrational? The actual situation at the site is very unclear; right now, nobody in the world, including you, can even assess the probability of Tokyo becoming increasingly irradiated, or of a criticality accident, in the coming week; and the Japanese government's and Tokyo Electric's shameful avoidance of disturbing the public with the scary details they do have only exacerbates the (rational, I'd argue) fears that already exist. Comet Tuttle (talk) 17:07, 17 March 2011 (UTC)

(ec) A better question would be why people have an irrational belief in the safety of nuclear power. Put simply, nuclear power isn't safe and it never has been. Even when operating correctly, nuclear power plants produce radioactive waste that will be dangerous for the next 10,000 years. A Quest For Knowledge (talk) 17:08, 17 March 2011 (UTC)

I think the question is why people seem to be more afraid of a rare leak of radioactive carcinogens from a nuclear plant than they are of the routine dumping of radioactive carcinogens into the air by coal plants; and seem to be more upset about a 1% increase in lifetime cancer risk for the nuclear workers than about the horrible lung diseases and fatal accidents that routinely afflict coal miners; and seem to be more afraid that a nuclear plant will render a hundred square kilometers uninhabitable than that coal plants will stop the gulf stream and render all of Western Europe unsuitable for agriculture. People do worry about those things, but I'm not sure that will stop them from demanding the closing of nuclear plants after this disaster, which will inevitably (as far as I can tell) lead to an increased demand for fossil fuels at a time when we desperately need the opposite. That's my fear. -- BenRG (talk) 20:15, 17 March 2011 (UTC)

There is quite an advanced literature on risk perception, esp. in relation to nuclear power. In particular you might find the work of Paul Slovic quite interesting — he charts out how fears of technology generally chart onto two axis: "unknown risk" and "dread risk". "Unknown risks" are things that are invisible hazards, with delayed effects, or exceptionally new. Think contamination, poisoning, irradiation. "Dread risks" are global, uncontrollable, catastrophic, involuntary. Think big disasters, or small disasters that you feel like you can't control. If you plot out how people judge various hazards on this scale, you get a nice graph of risk perception. On the bottom left (low dread, low unknown) are actually some quite dangerous things: bicycles, home electrics, automobiles, smoking (all things with very local effects, where you feel "in control", where by itself, one "accident" isn't going to kill more than a person or two). On the top right (high dread, high unknown) sits all of the radioactive fears (waste, weapons, meltdowns) — they trip up our psychological systems in a big way, and we've always viewed them (even before nuclear power) in rather mythological terms. Humans have ancient stories about evil rays, contaminated lands, and deformed children — the nuclear threat fit into these fears quite nicely. (On this point, my favorite book on the subject, though it is now a few decades out of date, is Spencer Weart's Nuclear Fear: A History of Images.) Note that I have generalized quite a bit regarding that chart. Weapons actually are somewhat less "unknown" than waste/power related things.)

None of this is correlated at all with what we might call actual risk (which can be tricky to calculate, but let's assume it exists). (This is not to say that all things considered dangerous are safe, or vice versa. Just that there isn't necessarily a meaningful correlation here in any individual case.) It is psychological. It is not a straightforward case of people not being "educated" enough on actual risks — that can itself backfire quite heavily (if you say, "it's safe, it's safe, it's safe!", and you're wrong in a BIG WAY one time... then your credibility is shot, and it's worse than if you hadn't said anything). Anyway, it is an interesting field. Whether people's risk perceptions are "rational" or not is entirely beside the point: human beings are not "rational" when it comes to our fears, and wishing they were will never make that so. --Mr.98 (talk) 17:15, 17 March 2011 (UTC)

An excellent way to assess risk in a rational way is to attach a price tag to it and see what a free market does with it. It's called the insurance industry and they're pros at weighing the cost of paying a claim versus the likelihood of having to do so.

When private companies in the USA wanted to start operating nuclear plants they asked insurance companies to take on some of their risk. The pros at the insurance companies looked at the payout vs. likelihood equation and said "no thanks". The industry should have ended there, but unfortunately it was important enough to national self-esteem that Uncle Sam stepped in and said "you guys just stash away a little money for minor accidents and if shit ever hits the fan my taxpayers will pick up the tab".

When the nuclear industry can cover its own risks then you can fairly claim that its skeptics are irrational. --Sean 18:12, 17 March 2011 (UTC)

Sean, nobody wants to insure against rare, large losses because that's risky. Insuring against many frequent, small (at the scale of the insurance company) losses is safe; you can build a business on that. The market is great at some things, but it's terrible at pricing rare, long-term risks. The actual, scientific cost of nuclear power versus the alternatives is such that we have to keep building nuclear power plants. The government steps in in these situations because that's why governments exist: to do the things that the market does badly. I know there are people who believe that the market does everything well and governments should be abolished, but those people are wrong, just like the people who think that homeopathy works, etc. This is the science desk. -- BenRG (talk) 20:15, 17 March 2011 (UTC)

I'm pretty sure those people fleeing Tokyo are actually at a greater risk of being injured getting to the airport or the train station, than they are of being injured by a small amount of radiation. Astronaut (talk) 18:15, 17 March 2011 (UTC)

At the moment, maybe yes. But the situation is fluid, and if shit goes bad, which it can very quickly, it can go very bad. Thousands and likely millions of people had measurable and sometimes drastic health outcomes from the Chernobyl disaster, and while right now things are not Chernobyl bad, people may not want to be around when it does. To get back to answering the first questions, the real reason is that there is something in the general human psyche that fears disaster and catastrophe, that is events where dramatic and large damage occurs in the very short term, but does not really fear small, incremental, or common dangers which only show their harm in the long term after many years. Thus, people really fear plane crashes, but car crashes aren't that scary, since plane crashes, though rarer, are more dramatic and catastrophic. And people fear being fat even less than getting in a car crash, even though being fat is going to kill many more people, and cause much more measurably bad health outcomes than car wrecks will, if only because not many people die or get hurt instantly from being fat. It's the same deal with nuclear power vs. coal power. What worries people is not nuclear waste (even though THAT is the real danger), what worries people is their local nuclear power plant blowing up like a bomb and killing all of them isntantly. Coal power, which has very little danger of blowing up and spreading instant death around the country side, feels safer because of that reason, even though we know that it is actually worse for our health, and for the health of the earth, than Nuclear. --Jayron32 18:42, 17 March 2011 (UTC)

I'm not sure why you think waste is "the real danger." It is a difficult technical problem only because we'd like to be able to say that it will be totally containable for thousands of years. In the short term, dry storage of waste is extremely safe, providing you don't live right next to it. (Wet storage is a different question, of course.) The political difficulties of waste siting are vastly overblown compared to the technical risks. (Which is not to say there aren't technical risks, but they are very minor. You can see this when you look at the actual engineering assessments of the hazards — it's things like, "will 100 people get cancer in the next 100 years" — not great, but hardly public enemy #1.) --Mr.98 (talk) 19:04, 17 March 2011 (UTC)

It's relative danger, again. In the long term, in accumulative effects, more problematic outcomes are likely to occur from nuclear waste than from power plants blowing up. Nuclear waste may be more safe than say, coal slag or greenhouse gas emissions from ordinary cars, but it is also probably the more problematic part of the nuclear equation picture, when compared to the dangers of catastrophic nuclear plant failure. But because it is cumulative and slow moving, it tends to get ignored. The point is not that nuclear waste is either perfectly safe, or the worst thing ever to have occured to humanity; people want to paint the world in dichotomies like that, much as you just charactized my arguement. Its that, taken in comparison, we can say that nuclear waste is more problematic than some stuff (like say, plant failure) but less so than other stuff (like, say, smoking cigarettes). --Jayron32 19:41, 17 March 2011 (UTC)

I think I read (a WP article?) about the over-reporting of train crashes (rare, kill more, overall death rate lower) and car crashes. Seems to be similar here. Can't find it now, though. Grandiose (me, talk, contribs) 18:53, 17 March 2011 (UTC)

The world needs energy, and all have environmental impact. You decide:

• Oil: Greenhouse-gas pollutant, limited amount to drill safely, Deepwater Horizon and Exxon-Valdez.
• Coal: Dirtiest greenhouse gases, over 20,000 miner instant deaths per year (most in China, fewer in US, but major long-term health impact), and more radioactive than nuclear waste.
• Nuclear: only three major accidents in 60 years, extremely expensive start-up, but so far the only "wasteland" area is in Chernobyl - atmospheric radiation accidents disperse quickly.
• Hydroelectricity has major ecosystem impact and is not universally available or unlimited, as with renewables like solar, wind, and wave.

So indeed, take your pick. SamuelRiv (talk) 19:32, 17 March 2011 (UTC)

I disagree about the nuclear waste impact you've given, as we are still experiencing effects in the UK, hundreds of miles from Chernobyl: Chernobyl_disaster_effects#24_years_after_the_catastrophe. I also notice you refrain from mentioning the environmental impacts of renewable energy. --TammyMoet (talk) 21:27, 17 March 2011 (UTC)

I don't see that data on coal miner instant deaths in the article cited. Yes, it's dangerous, both in the ground and downwind, but would it be if we spent the kind of money we spend making nuclear plants "safe"? Wnt (talk) 23:41, 17 March 2011 (UTC)

If you spent that kind of money on coal, it would no longer be cost effective. Nuclear energy is far more cost effective, to start, allowing you to add lots of safety precautions and still have it be competitive. StuRat (talk) 00:23, 18 March 2011 (UTC)

I have never seen an economic justification for nuclear that includes the real cost to future generations of managing the waste. HiLo48 (talk) 07:06, 18 March 2011 (UTC)

Well, then, you'd have to compare that with the real cost to future generations of the alternatives. In the case of fossil fuels, that would include moving the populations of major cities on the oceans inland some 50 miles to deal with rising sea levels from global warming, or building massive dikes around them. I think that's several trillion dollars right there. Then there's the increased damage from hurricanes and tornadoes to consider. StuRat (talk) 07:31, 18 March 2011 (UTC)

The 'real cost to future generations' is usually negligible. Assuming an annual real rate of return of 7% (a conservative 10% growth, less 3% inflation) a dollar paid in 2050 is worth about seven cents today. A dollar in 2100 is worth about a fifth of a cent today. A dollar in the year 2500 is worth a bit less than a billionth of a cent. If one honestly figures the cost of processing and safely storing the waste for the next fifty or sixty years, then the real cost to store it forever is only trivially greater. TenOfAllTrades(talk) 13:55, 18 March 2011 (UTC)

I disagree. Yes, each dollar spent in 2050 will be worth less, but presumably more dollars will need to be spent in 2050 for the same activity as today. If the inflation rate of minding nuclear waste is the same as the general inflation rate, then they should cancel out. The only reason I could see why it would have a lower inflation rate is if electronics to detect radiation levels become relatively cheaper. While the cost of electronics does tend to fall relative to other items with time, radiation detectors may be an exception, since too much miniaturization (the primary driver of cost savings) may cause them to fail when exposed to radiation. As for your 10% annual economic growth rate, that's absurdly high, except maybe in China, but even there it's unsustainable in the long term. Perhaps you meant the 10% to be the returns from investing money now, say in the stock market, to cover later costs ? That logic would only apply if such investments were actually being made, and, even then, one would need to consider the opportunity cost versus investing that money elsewhere. StuRat (talk) 18:47, 18 March 2011 (UTC)

I'm not sure you understand how future costs are evaluated (and discounted) for the purposes of making comparisons between expenditures that occur in the future versus those which take place immediately. As to whether or not such investments are being made, for the United States, at least, the Nuclear Waste Policy Act requires utilities to contribute to the Nuclear Waste Fund; the Fund currently has about $25 billion in assets. TenOfAllTrades(talk) 19:25, 18 March 2011 (UTC)

And is it currently invested in a financial instrument earning a conservative 10% growth per year ? StuRat (talk) 19:29, 18 March 2011 (UTC)

The data regarding yearly international coal miner deaths is taken from the "China" section. Official China Labor Bulletin statistics cite 6000 deaths per year, and the number is adjusted to reflect the vast number of mines with few or no records (particularly those of accidental deaths). Additionally, I get sources for 400 deaths/yr in the US from black lung disease, which of course is an immediately-identifiable etiology (as opposed to cancer). I don't mention environmental impact of renewables, just that they can't be tapped wherever and whenever you want and thus will not replace all power, but you're right that like anything else they have environmental impact as well. Regarding long-term Chernobyl effects outside of the immediate area, fair enough. I will note, though, with respect to the compare-two-evils fallacy, that the amount of atmospheric fallout from Chernobyl is negligible to that of the above-ground nuclear tests. Regarding investment, in the US where coal is king we invest heavily in safety, which is why miner deaths per year has gone from thousands 50 years ago to 30 today. SamuelRiv (talk) 00:45, 18 March 2011 (UTC)

I am skeptical that China really has ~13000 deaths a year from coal mining that they don't know about; [18] sounds like a confident source. Obviously 6000 deaths is already intolerable, and perhaps the question of nuclear power in China might go a different way. Then again, Nuclear power in the People's Republic of China is only 1% currently, and who knows how it will work out for them (especially in the same poor regions of the country)? Wnt (talk) 01:51, 18 March 2011 (UTC)

The answer to the OP's question is quite simple. People display irrational behavior because people are irrational. Does that really surprise anybody? Dauto (talk) 23:57, 17 March 2011 (UTC)

Displaying an irrational fear takes a lot less effort than learning the science so that you can display a rational fear. HiLo48 (talk) 00:04, 18 March 2011 (UTC)

That's just a tautology. It fails to explain why the nuclear fears touch off such irrationality in particular. --Mr.98 (talk) 02:08, 18 March 2011 (UTC)

My point is that people in general are irrational just about all the time, so it is not surprising that they are also irrational about that particular subject. Dauto (talk) 12:55, 18 March 2011 (UTC)

Some thoughts as to why nuclear power feeds irrational fears:

1) Radiation is invisible. Thus, people don't believe when politicians and "experts" tell them everything is safe. If radiation was visible, they would know if an area was safe or not. Perhaps if everyone had Geiger counters, they would feel safer, both because they would know if radiation levels went up, and would realize that there's background radiation everywhere, and it's nothing to worry about. Maybe portable pollution detectors would also be a good idea, so they would know when they are in an areas of (fossil fuel) air pollution, and would see how much worse that problem is.

2) Nuclear waste is concentrated, versus fossil fuel pollution, which is widely distributed. It's easier to point to a barrel of nuclear waste and think "that's dangerous" than to point at the sky and think "that's dangerous". If, at some point, fossil fuel pollution is also concentrated into barrels of toxic waste, then this difference may disappear, when people compare millions of barrels of FF waste with a few of nuclear waste. StuRat (talk) 00:32, 18 March 2011 (UTC)

I think of several things:

• Nuclear power is very expensive if you calculate the absolute cost. Reprocessing is extremely expensive. Storage for 10000 years is also very expensive. It only works when the military and the government pays for the expenses.
• I like to imagine a conflict like that in Libya in a country with a lot of nuclear power plants. All people leave and one after the other explodes. Or in like in Yugoslavia. When one party shells the nuclear power plant instead of a bridge. Or like in Egypt. When after an election a fundamentalist government Israel bombs the power plants as a friendly first gesture.--Stone (talk) 08:15, 18 March 2011 (UTC)

Bombing a neighbor's nuclear plants isn't a good strategy, as the radiation would be likely to spread back to you, and also piss off other neighbors. Terrorists, on the other hand, might not care if they poison everyone, although PR is still a concern, even for them. I have always been an advocate of building nuclear plants more safely, though, such as in old mines, far from population centers (the cooling towers can still be above ground, but the radioactive portions should be safely hidden). The nuclear waste can then be kept in the mine permanently, after the plant is decommissioned. This does require transporting the power further, with more losses, but this cost can be justified both by improving public safety and preventing the nuclear power industry from suffering these periodic black eyes which threaten to destroy it. In an age of terrorism, we have yet another reason. The distant, underground construction also gets by the NIMBY problem. StuRat (talk) 17:56, 18 March 2011 (UTC)

A recent (er, future...?) piece in the New Yorker ("The Nuclear Risk," March 28 2011) also discusses the general issue of risk assessment of nuclear energy, concluding: "As the disaster in Japan illustrates, so starkly and so tragically, people have a hard time planning for events that they don’t want to imagine happening. But these are precisely the events that must be taken into account in a realistic assessment of risk. We’ve more or less pretended that our nuclear plants are safe, and so far we have got away with it. The Japanese have not." WikiDao ☯ 17:13, 18 March 2011 (UTC)

Elastic - is it okay to keep it stretched?

I need to know how bad it is for elastic to be kept it in its stretched state for a very extended period of time. Thanks. 71.220.225.153 (talk) 19:49, 17 March 2011 (UTC)

I'm not sure if that would effect how long it will last, as, for many elastomers, "aging" is due to mainly exposure to UV light or evaporation of volatile components. However, one concern is that when it does finally give way, it may injure somebody, say by snapping them in the eye or dropping whatever it was holding. Can you tell us what you had in mind as far as the type of elastic and load ? StuRat (talk) 00:09, 18 March 2011 (UTC)

I recently bought a bandoleer to hold a bunch of shotgun shells. The holders for the shell are made out of elastic and I was going to store the bandoleer with shells loaded in it unless it would wear out the elastic and make it unusable. As of right now I'd say the elastic is far too tight. It is fairly difficult to get shells in and out of it. 71.220.225.153 (talk) 05:43, 18 March 2011 (UTC)

Well, then you want to stretch the elastic, right ? I think that might work. However, certain types of elastic might also leave residue on the shotgun shells, as the elastic deteriorates, and this could interfere with performance when the shells are used. A safer approach might be to remove the shells, and replace them with something as large or larger, like rolled up newspaper bits, to do the stretching. A similar method is often used to help shoes in storage keep their shape. StuRat (talk) 07:22, 18 March 2011 (UTC)

Virgil C. Summer

who was Virgil C. Summer? a nuclear plant is named after him?? — Preceding unsigned comment added by Timc321 (talk • contribs) 20:01, 17 March 2011 (UTC)

He was a president of the South Carolina Electric and Gas Company, see [19] for a very brief statement as such. Since they built and own said nuclear plant, it makes sense they would name it after a former president of the company. --Jayron32 20:16, 17 March 2011 (UTC)

And this Google Books search turns up a few more scanty refs: [20]. --Jayron32 20:19, 17 March 2011 (UTC)

I've added a reference (from SCANA's own website) to that effect to the Virgil C. Summer Nuclear Generating Station article. Unfortunately there's no more worthwhile info, beyond what Jayron32 has found already, there. -- Finlay McWalter ☻ Talk 20:27, 17 March 2011 (UTC)

High oxidation numbers: above 8?

Is there any reason why transition metals' oxidation numbers always seem to cut out at eight (in group 8 elements)? For instance, why can't you get nine on a group 9 element (I'm thinking rhodium, iridium, possibly also americium where the d electrons are replaced with f) to make it d⁰? Like say iridium(IX) hydride (IrH₉), which is isoelectronic with the real complex ReH₉^2–. Or I could certainly imagine a hyper-periridate anion IrO₅^–. Os(VIII) forms readily and it's nearly identical. (Feel free to get really in-depth; I'm three years into a chemistry masters degree.) 137.205.222.209 (talk) 20:40, 17 March 2011 (UTC)

Might if have to do with the geometry of 9-ligand complexes? Once you get over 6 ligands, the Octahedral molecular geometry, things get weird. There are occasional higher order bonding schemes, like Pentagonal bipyramid molecular geometry but they are quite rare. You almost never find bare transition metal ions in solution or in crystal networks, especially with the higher oxidation number metals; even low-oxidantion number metals like copper-(I) and copper-(II) form complexes very regularly. Admitedly, my chemistry is a bit older than yours, since you are in it, and it's been 15 years or so for me since I studied this stuff in depth. There's probably some combination of electrostatics and orbital geometry that makes high oxidation number transition metals to be highly unlikely. The article Ligand field theory hints on some of the problems with considering what happens in d-orbitals; at first approximation, and under normal circumstances, all 5 d-orbitals are degenerate, which is true energetically, but in real bonding situations, the three d(xy), d(xz), and d(yz) operate differently than do the d(z²) and d(x²- y²) orbitals. Making a WAG, my guess is that due to these differences in d-orbital organization, there's some barrier towards, say, removing all 9 electrons from the 6s and 5d electrons in Iridium; in other words theres something in the way that the d-orbitals are organized that presents a large jump in ionization energy between the 8+ state and the 9+ state. f-electrons are so deep, I doubt they participate to any great end in hybridization, in bonding, or in ion formation in the way that s, p, and d orbitals can. Again, this is just me riffing on my admittedly underused 1990's era inorganic chemistry knowledge... --Jayron32 02:32, 18 March 2011 (UTC)

More than just that they "seem to cut out at eight" (emphasis mine), that is citedly the actual highest known (at least as of a little over a year ago), although there are groups studying that limit. See for example doi:10.1002/cphc.200900910. DMacks (talk) 03:05, 18 March 2011 (UTC)

Deliberate meltdown

Lets say some psycho wants to create a doomsday device. What would happen if someone made a reactor that had no coolant, turned it on full power, and deliberately let it meltdown. Could this have global effects or would the effects be relatively localized near the point of meltdown? ScienceApe (talk) 20:41, 17 March 2011 (UTC)

Basically what you are describing is a type of dirty bomb. Looie496 (talk) 20:57, 17 March 2011 (UTC)

There are two hugely relevant variables. How large is the device, and where is it located. Googlemeister (talk) 20:58, 17 March 2011 (UTC)

A meltdown would certainly be no worse than a nuclear bomb with the same amount of material. The nuclear bombs used, either for wars (hiroshima) or for Nuclear weapons testing, do not appear to have had global effects. 83.134.176.57 (talk) 21:08, 17 March 2011 (UTC)

You really cannot compare reactor meltdowns and nuclear weapons. (What do you even mean by "the same amount of material" in such a comparison? Reactors use tons of fissionable materials; nuclear weapons use kilogram quantities.) The comparison is highly misleading in every way. They are very different types of events. The only similarity is that both involve distributions of fission products. And there is some dispute as to whether the years of atmospheric nuclear testing did have global effects (e.g. increased thyroid cancers, etc.). They certainly had national effects. But again, this is kind of irrelevant, because it tells you very little about meltdowns. --Mr.98 (talk) 21:28, 17 March 2011 (UTC)

This is essentially what happened at Chernobyl, albeit not "mad men" so much as "fools." The acute effects are "regional" — not global, but certainly not just "local". There are some "global" effects, but they are very hard to measure (statistical up-tick in cancers, for example — hard to figure out what the causes of those are). --Mr.98 (talk) 21:28, 17 March 2011 (UTC)

The cobalt bomb was proposed as a similar device; one could translate its principles into a reactor, but a bomb would be more effective at creating and distributing the fission products. I believe (the article doesn't mention it, but its references do) that one advantage of such a device would be that it would not have to be transported to the target and could be arbitrarily large, providing, of course, that the device is understood to be a "doomsday weapon." Acroterion _(talk) 21:37, 17 March 2011 (UTC)

After encountering cobalt bomb, I ran across some unusual claims that the Russians had actually built a Doctor Strangelove type device. These emanate from Bruce G. Blair. I encourage anyone to take a look at the evidence and try to figure out if this is plausible or not; I've added a brief mention of what I found in the article. Wnt (talk) 00:28, 18 March 2011 (UTC)

He's referring to Perimetr, the so-called "Dead Hand" system. It's not really the same thing as the doomsday device. It was a command and control system that would allow the top Soviet leaders to say, "we're in a very tight time, and nuclear war could start any minute, so if you need to, launch the bombs." Then the Soviet army heads could, if they felt things were really bad, could say to a specific base, "look, if you lose contact with us, assume we're toast, and launch the nukes." Then the specific base would send up a special ICBM that had a radio transmitter on it that would say to all of the other ICBM bases, "go ahead and launch 'em, boys!" and then they'd all launch at the USA or whomever. So it's that last bit that makes it sound Strangelovian — it's a one-way trip at that point if a bomb goes off (or if for other reasons they lose contact). But it's a few more steps than that. The reason to make it was not some sort of MAD pact; it was due to the fact that in the 1970s the Soviet army realized their leaders were a bit dotty (Brezhnev and Chernenko being the obvious ones) and might not be able to order the nuke attack if it came down to it, and also they realized that a very weak point in the Soviet ICBM system was the communication system between individual missile bases. (For more information, I heavily recommend David Hoffman's The Dead Hand, which came out a year or so ago, and is pretty well-researched. --Mr.98 (talk) 01:28, 18 March 2011 (UTC)

Ach! I got hit by the oldest trick in the book that time. The first 'sources' I came across in the blogosphere made it sound like the system set off cobalt bombs automatically, but the ones closer to the source I actually cited didn't actually make that link, even though they talk about both things. (They're just both reminiscent of Doctor Strangelove. That one catches me more than any other. Wnt (talk) 01:41, 18 March 2011 (UTC)

I've run across references (don't ask me where, it's been a while) to a similar last-ditch American system, going by the codename Last Dance. Acroterion _(talk) 02:09, 18 March 2011 (UTC)

Just a pointer - I once read an article on history of nuclear wepons. According to it at first the concept existed, but no one was sure how it should look like, so some developed concepts similar to nuclear reactors (it seems everyone might have used reactors to explore the process, but I think it said that Nazis at least wanted to make an acctual bomb that way) ~~Xil (talk) 10:36, 18 March 2011 (UTC)

It's true that the initial conception of a nuclear bomb by Heisenberg was something in between a reactor and a bomb. But it was very ill-conceived, and was reflective of the fact that they didn't realize they could do a fast-neutron chain reaction. There is a lot on this in Heisenberg and the Nazi atomic bomb project by Paul Lawrence Rose (he calls it the "reactor-bomb" if you want to skim through the Google Books edition). --Mr.98 (talk) 12:54, 18 March 2011 (UTC)

March 18

Breast milk and iron

According to this site: [21], human breast milk is almost devoid of iron, and many other vital nutrients. So then, how do babies which are exclusively breast fed get their iron, and those other nutrients ? StuRat (talk) 00:40, 18 March 2011 (UTC)

They store it before they are born. Especially non-c section babies get filled with extra blood from the placenta by the contractions (sometimes causing jaundice when the extra blood is broken down). The iron in blood is almost completely recycled, and the store of iron lasts them till they start eating solids. Ariel. (talk) 00:44, 18 March 2011 (UTC)

Where is this "excess blood" stored ? Even with perfect recycling, they would need more iron to account for their growth. And, if babies can recycle iron so well, why can't adults (especially men, most of whom don't menstruate :-) )? Why do adults need dietary iron ? StuRat (talk) 03:32, 18 March 2011 (UTC)

(edit conflict)Two things:

1. When reality seems to be in conflict with "experts", trust reality. In this case, since humans for millions of years fed their infants breast milk, and yet we as a species survived; and since today, still, the majority of humans still feed their infants breast milk, and those babies keep growing into healthy adults, there must be something right about breast milk. Regardless of what the "label" says, or the list of ingredients or anything else, its not that breast milk is deficient, it must be that what you are presupposing to be necessary OR what you are presupposing to be actually in breast milk, per that label, is really there, that is what is deficient. Breast milk is not deficient, obviously, so we need to figure out what is going on here.
2. Read the label again. The % of iron is the % of the daily requirement an adult eating a balanced 2000 calorie diet would get out of taking in 172 of those calories in breast milk. Instead what you have is an infant, who is eating much less (say 500 calories or less), and getting all 500 of those calories from the breast milk. In that case, the infant may be getting 100% of their daily requirment for iron, since a) their iron requirements are likely different b) American food labels are rounded somewhat, so what might be, say 0.44% for an adult would still show up as zero. That doesn't mean there is no iron, just a small amount when compared to an adult requirement, but likely suffient for what an infant needs. And that is all dependent on the fact that you can trust what that website is telling you...

That's how I read the situation. (post EC extra stuff) what Ariel said makes sense regarding how infants work out their iron situation. Makes sense. I knew it had to work out, because of point 1.--Jayron32 00:54, 18 March 2011 (UTC)

To your point 1, if a baby has only 1/4 the calorie requirements, and also only 1/4th the iron requirements, then 0.44% of an adult RDA would become 1.76% of a baby's RDA, still grossly insufficient. And I suspect that more iron is needed, proportionally, when growing, than as an adult. StuRat (talk) 03:28, 18 March 2011 (UTC)

Apparently not; again your assumption that small babies need, proportionally, the same amount of iron as adults is not borne out by the fact that breast fed babies aren't all dead, and are perfectly healthy, even with regards for the kinds of reasons that, you, as an adult, need iron. Breast milk is empirically not deficient, so either a) that "nutritional facts" label is wrong or b) babies need a lot less iron in their diets than adults. Ariel, above, provided ample evidence that the real answer is b, though I have my suspicions that there may be some option a at play as well. Again, you can't start with the supposition that breast milk is deficient when there's ample empirical evidence (nearly all of humanity for all of history; indeed even more than that, we have nearly all of mammalia for even longer). The experiment has been run trillions upon trillions of times and milk works. So we have to rephrase the question: What in your supposition is wrong, or what is it about how babies need iron that is different than adults? Ariel answered that succinctly: they don't need dietary iron during their first several months because of the massive iron boost they get during normal birth. --Jayron32 03:50, 18 March 2011 (UTC)

It's patently obvious that it has to work out somehow, so stating that over and over doesn't help much. I want to know HOW it works out. The only assumption I made in my initial post is that the nutrition site I listed has correct info. If you have another site which disputes that info, then that would be useful. If babies are born with "excess blood", I'd like to see a site which supports and describes that. Also, I believe some cultures have babies who are exclusively breast fed for years, so how can the iron last that long ? StuRat (talk) 07:11, 18 March 2011 (UTC)

The extra blood is stored as rather red-looking babies (at first, till the excess red blood cells are digested in the spleen). Iron is also be stored in the liver and other places from before they are born. Normally elements diffuse from a higher concentration to a lower across the placenta, but iron is actually pulled against the gradient if necessary (potentially leaving the mother anemic). This iron is then stored. The primary loss of iron is mucousal irritation of the bowels (red blood cells are recycled basically perfectly in the spleen), but that doesn't happen to breastfed babies, so their need is lower. That's one of the reasons their feces have such a strange (light) color. This page says more or less the same things: http://www.kellymom.com/nutrition/vitamins/iron.html It also mentions that breastmilk is not as deficient as it might appear - the iron is in a form that is extremely well absorbed. Normally an adult will need 20-100 times as much iron in their food as they actually need since it's so poorly absorbed, but in breast milk you only need twice as much. The net result is that breastmilk effectively has 10 (or more) times as much iron as it might appear. Ariel. (talk) 11:53, 18 March 2011 (UTC)

Thanks. It looks like human breast-milk is still deficient in iron, even after the better absorption is considered, since babies do gradually use up their excess stores. Do children in societies that breast-feed longer suffer from anemia ? Has anyone attempted to create iron supplements in the more absorbable form, similar to breast-milk ? Do any other mammals create such milk ? StuRat (talk) 17:44, 18 March 2011 (UTC)

Yes, they do eventually run out, but by then they are eating solids. I don't think even in those societies that it is exclusive, but rather it's a supplement. Presumably they would get iron from the other foods they eat. It looks like Iron Glycinate (or any iron attached to an amino acid) is best absorbed. It's also important to eat the iron together with vitamin-c. Ariel. (talk) 18:27, 18 March 2011 (UTC)

There's an advert for a toddler follow-on milk on British TV which goes on about how little iron breast-milk has and how much their product has, conveniently ignoring the fact that toddlers will (or should) be eating a varied diet including several sources of iron, and not relying only or mainly on milk. DuncanHill (talk) 12:08, 18 March 2011 (UTC)

How the following time dilation senario in three frames of reference can be explained?

Let we have A and B transparent spaceships such that B is inside back of A as the size of A is greater than B. Also there is an observer at the middle of A who is stationary for B.

Now both spaceships ignited and set out at same time (with speed close to the speed of light) for space journey. The front of A is open so that B may leave A if want. The reading of speedometer of B may or may not be the same with that of A. Light clocks installed in each ship with top and bottom mirrors,  is also starts automatically with ignition.  

We have following three reference frames

1-  within B (with light clock LC2)

2- within A (with light clock LC1 and moving spaceship B in which LC2 is installed)

3- for outside observer who is not co moving on asteroid

Now

1- LC2 is making time dilation triangle for (a) for observer at the middle of A who is stationary for B (b) for outside observer who is on asteroid.

2- LC1 is making for (a) for outside observer on asteroid (b) may be for onboard observer B.74.198.150.213 (talk) 02:48, 18 March 2011 (UTC)Eccentric Khattak#1

I think I understand the setup, but what is the question? You only asked "how can it be explained?", which is not specific enough. -- BenRG (talk) 03:25, 18 March 2011 (UTC)

Then you understand more than me. The explanation above about the setup is quite confused in my opinion. Dauto (talk) 03:48, 18 March 2011 (UTC)

I don't understand what the point is of making the spaceships transparent or allowing one to enter the other. Couldn't they simply be normal spaceships that pass by one another? More to the point, can't you just say that A is the surface of the Earth and only look at B (i.e. usual twin paradox?) But I don't understand the acceleration that A and B might undergo. Wnt (talk) 05:34, 18 March 2011 (UTC)

I don't know what it is that you want to know or you have trouble understanding, but maybe you should have a look at Bell's spaceship paradox. If you are asking whether 2 spaceships, initially at rest, and starting at the same time with the same acceleration, are moving relative to each other while they are accelerating, then the answer is yes (specifically, in the reference frame of an observer at the position of one spaceship with the velocity of this spaceship at any point in time while they are accelerating, as we only look at non-accelerating reference frames). Icek (talk) 08:07, 18 March 2011 (UTC)

I want to make it a little more clear if all above is incomprehensible. Let Spaceship B is at rest  in A while  A is moving with speed close to the speed of light. When A is about to pass by an asteroid,  B take off in A in the same direction. Thus an observer at middle of A will see a ship B is moving with light clock LC2 in his frame of reference. An outside observer will see B is moving in moving reference frame  (with light clock LC1)  of A. The direction of both A and B is same. Thus there are three reference frames

1- Within B (with LC2) 2- Within A (with LC1 and moving ship B) 3- For outside observer (with moving A inside which B is moving).

My question is how the aforementioned clocks (two time dilation triangle) can be analyzed w,r.t both onboard observers, observer at the middle of ship A and outside on asteroid. 

I don't know how to post a question with diagram therefore it's a little confusing but I hope I have explained things clearly enough for you all  to understand74.198.150.213 (talk)Eccentric Khattak#1 —Preceding undated comment added 23:09, 18 March 2011 (UTC).

Is spaceship A accelerating? Anyway, you can always analyze the situation by applying the Lorentz transformation to the time and space coordinates (and if you are specifically asking what the velocity of B is with respect to the asteroid if you only know the velocity of A with respect to the asteroid and the velocity of B with respect to A then you can use the velocity-addition formula). Icek (talk) 12:37, 19 March 2011 (UTC)

It makes no different whether one spaceship is inside the other. The analysis is the same as if they were side by side. Does that help? -- BenRG (talk) 20:31, 19 March 2011 (UTC)

Efficiency of nuclear reactor

Hello, What % of the heat generated by a nuclear reactor is converted to electricity?(whats the efficiency of the turbine-cooling circuit i mean) TY DST DSTiamat (talk) 08:53, 18 March 2011 (UTC)

See the list at List_of_BWRs. For example, the Fukushima Daiichi reactor 1 had a MWth of 1380 and a MWe of 460, or 33% efficency. F (talk) 10:22, 18 March 2011 (UTC)

The efficiency is usually in the range of 30 to 35 percent which is the same efficiency of a coal power plant since they work the same way, only with a different source of heat. Dauto (talk) 12:44, 18 March 2011 (UTC)

Some of the newer designs are above 40%. Dragons flight (talk) 16:25, 18 March 2011 (UTC)

Radiofrequency ablation for typical atrial flutter

Is there any term which is addressed by "drag and burn" and it is related to cavotricuspid isthmus. Cavotricuspid radiofrequency ablation for typical atrial flutter is a proceudre and something on the lines the term "drag and burn" gets mentioned. Is "drag and burn" the right term, or there is something else related to the radiofrequency ablation for typical atrial flutter and Cavotricuspid. aniketnik 10:27, 18 March 2011 (UTC) — Preceding unsigned comment added by Aniketnik (talk • contribs)

I'm not sure I understand the question. The term "drag and burn" is widely used in the literature for a method of pulling a probe across the atrium in a linear series of steps and creating a lesion at each point. My understanding from a Google search, though, is that the technique does not work very well and is not widely used. Looie496 (talk) 17:13, 18 March 2011 (UTC)

Resource starvation or Maximum throughput scheduling for doing office paperwork?

I spend nearly all my working hours doing non-routine paperwork. The paperwork varies in importance. Doing the most important things (which also require the most time to do and are the most difficult) would result in not being able to do anything else for months, as described in the Resource starvation article. Currently I do Maximum throughput scheduling where I do the quick easy jobs. However this leaves the big difficult jobs undone.

What method of scheduling should I use, that does not have the diadvantages of the two extremes above? Thanks 92.15.2.23 (talk) 11:54, 18 March 2011 (UTC)

This reminds me of the Time Manager scheduling system, used by an IT department I used to work for. It involves setting goals, identifying key tasks identified with each of these goals along with milestones and deadlines, and scheduling tasks associated with each of the goals every day until the deadlines/milestones were met. (As far as I understand - you see I was a mere untrained secretary...) You might like to investigate this further. --TammyMoet (talk) 12:46, 18 March 2011 (UTC)

Which tasks, if left undone, will prevent other employees from doing their work? Which bits of paperwork are likely to have the most (and least) serious consequences for your employer? Is there a reason why you can't break up your day or week into blocks of time which can be allocated to different tasks, instead of your described all-or-nothing approach? (Do long-term projects in the morning while you're fresh, and do the quicker tasks in the afternoon. Or make Monday through Wednesday 'major project' days, and do small stuff Thursday and Friday. Or whatever.) Which tasks do the supervisors who evaluate your performance think are most important? Seriously; the people who pay your salary get the ultimate say in your work priorities—what happens if you ask your boss? TenOfAllTrades(talk) 13:05, 18 March 2011 (UTC)

There is nobody else - just me. No other employees, no supervisor, no employer, but only me. 92.15.2.23 (talk) 13:53, 18 March 2011 (UTC)

Ah, so your question is really "How do I do twelve hours' work in eight hours per day?" The answer, of course, is "You can't." At least, not forever. Either find a way to reduce/streamline the workload, hire additional help, or subcontract some tasks. It's difficult to advise you further without knowing what line of work you're in. TenOfAllTrades(talk) 16:55, 18 March 2011 (UTC)

Maybe the single machine/total tardiness sections of Scheduling: theory, algorithms, and systems By Michael Pinedo might be of interest. Sean.hoyland - talk 13:48, 18 March 2011 (UTC)

I had a similar situation, for writing computer programs, although I did have a boss. They gave me so many assignments they knew I couldn't do them all, and they realized I couldn't do all of them, but they did allow me to set my own priorities. I decided to write those programs which I found most enjoyable, and leave the rest to fester. StuRat (talk) 17:30, 18 March 2011 (UTC)

I think you already answered your own question by saying certain tasks were "most important". The only alternative consideration is whether you value getting more tasks done or more important tasks done. But as long as the less important (though perhaps more numerous) ones don't block other work (even your own) then I say let 'em fester, since by definition they are not as important as the other ones to accomplish (and as others noted, you apparently cannot get it all done). DMacks (talk) 17:53, 19 March 2011 (UTC)

How much warning of the Japanese tsunami was given?

Did the coastal Japanese get any prior warning of the tsunami, or was it unexpected? If yes, how long did they get? I appreciate that even if an official warning was given, not everyone may have recieved it in time. Thanks 92.15.2.23 (talk) 12:36, 18 March 2011 (UTC)

I don't know, but the quake was a warning in itself. --85.77.4.120 (talk) 14:20, 18 March 2011 (UTC)

The news reports I heard said that in the hardest hit areas, a tsunami warning was immediately and automatically issued as soon as the earthquake struck. The tsunami then first hit land only 15 minutes later. 148.177.1.210 (talk) 14:24, 18 March 2011 (UTC)

Some places had more than a half hour warning. Rmhermen (talk) 14:41, 18 March 2011 (UTC)

How much radiation protection from an Armored car (military), Armored Personnel Carrier or Tank?

I understand that modern APCs and tanks are sealed from chemical weapon attack. How much protection from radiation would a modern tank, armoured car or APC such as the Type 96 Armored Personnel Carrier give? I'm wondering why they are not being used to drag fire hoses to approriate positions in the Japanese nuclear emergency. Thanks 92.15.2.23 (talk) 12:43, 18 March 2011 (UTC)

I don't think they need that level of radiation protection to drag hoses. Around the plant, it is not "zap you dead" amounts of radiation, it is "the equivalent of lots of chest x-rays" amount (and the latter, while not good, is still only a probabilistic rise in the chance of developing cancer). The people who are probably getting way too much are the people working in the control rooms (where they are getting a year's allowed exposure in an hour, and sometimes having quite dangerous spikes of radiation), not the people dragging hoses around. I don't think the nature of the problem is not being able to drag hoses around, either. --Mr.98 (talk) 13:24, 18 March 2011 (UTC)

I wonder if there is any such thing as anti-radiation armour? It would be heavy. Radiographers in hospitals wear an apron, perhaps lead-lined. 92.15.2.23 (talk) 13:56, 18 March 2011 (UTC)

I don't think the heroic workers and fire fighters on the Japanese reactors site are at risk of being zapped by bursts of gamma rays or X-rays. Long-term health risks arising from contanimation from fallout must be a bigger concern. In this respect, the best prophylactic measures are surely a well filtered or self contained air supply and thorough decontanimation procedures. Gandalf61 (talk) 14:12, 18 March 2011 (UTC)

There is certainly radiation outside the buildings (hence the evacuation of most workers, the suspension of outside work several times during radiation spikes, etc.) There also is certainly gamma radiation - and alpha and beta. Their suits and respirators are only to keep radioactive particles off their skin and out of their lungs, altough they will stop alpha and some beta. Mainly the suits are so they don't need to be decontaminated so often. Rmhermen (talk) 14:41, 18 March 2011 (UTC)

Some tanks, such as the Abrams M1, have depleted uranium armour, but that's intended for extra resistance to armour-piercing projectiles, not gamma radiation. The primary radiological hazard isn't radiation external to the vehicle (there aren't nuclear bombs going off or big chunks of gamma emitters lying around. The danger is instead from particles of radioactive material getting onto people and contaminating surfaces: these are carried in the plume from a burning reactor (which is why the exposure in helicopters above the reactor is so great) and they fall out onto the land under the plume. Modern main battle tanks have air filtration systems and some (such as the Abrams) run an overpressure a/c system (fed through extensive filters) which are designed to keep out smoke, chemical agents, sand, dust, and other contaminants. Those fitted for urban or desert warfare have yet more filtering. But a tank is massive, and incredibly heavy, and the places to which the water needs to be delivered are inside ruined buildings. So instead they're using military fire engines - I think that means modern aviation-style ones, which have hoses on turrets that can be operated without the firefighter leaving the cabin, and have air filter systems designed to allow them to operate close to burning aircraft (which should help to keep out those radioactive particulates). -- Finlay McWalter ☻ Talk 14:27, 18 March 2011 (UTC)

I understood that the helicopter pilots problem was that they were in a direct-line from the gamma emmisions from the exposed fuel rods in the spent fuel tanks (now that the building roofs are gone while those on the ground are still somewhat protected by the large mass of the concrete pool walls. Not sure how absorbtive concrete is, though, maybe they are lead-lined as well? Rmhermen (talk) 14:41, 18 March 2011 (UTC)

Lead is only a little more effective than concrete. A 10 cm layer of either of them will be quite effective to block most gamma rays. (Equivalent to about 1 km of air). Dauto (talk) 00:48, 19 March 2011 (UTC)

It appears they are steel-lined anyway. Rmhermen (talk) 04:55, 19 March 2011 (UTC)

Levels of 400 millisieverts per hour of radiation were reported at some time during the past week. That does pose an immediate radiation hazard, with radiation sickness likely after 2.5 hours of exposure. This is aside from any danger of inhaling particles, ingesting them, or taking them home on your clothes. A tank may have thick armor on the turret and parts of the hull, but the floor is typically quite thin, and radioactive isotopes on the ground would "shine" through the bottom and harm the personnel inside if they stayed there very long, unless the tank provided shielding or unless shielding such as lead plates were added. Radiation protection says that 2.5 cm of steel would cut the radiation in half, the same as 1 cm of lead, 0.2 cm of depleted uranium, or 6 cm of concrete. Cutting the dose in half would mean radiation sickness after 5 hours rather than 2.5 at the extreme hotspot. More thickness would give proportionately more shielding. M1 Abrams#Armor says it has "chobham armor," layers of steel, ceramic, plastic and kevlar. Only the steel would provide much shielding. The article says some tanks have depleted uranium mesh only at the front of the turret and front of the hull, not particularly helpful if the radiation is coming from stuff on the ground under the tank. Armoured personnel carrier says "Armour on APCs are usually composed of simple steel or aluminium, sufficient for protection against small fire arms and most shell fragments." Thin steel or or around an inch of aluminum armor way would provide only slight reduction in the radiation the crew was exposed to. The M113 APC had 2.86 cm of aluminum on the floor and 4.45 cm on the top.I could not find a ref for the thickness of aluminum to cut the ionizing radiation dose in half. The best bet would be to operate a device remotely. Howe & Howe Tech has converted many of their tracked vehicles to full remote control, for firefighting or combat applications, and the nuclear industry would do well to similarly develop remote operated firefighting, demolition, and observation equipment. You do not need a human in the cab of a crane, or behind the wheel of a firetruck, to operate the hydraulic controls to move the vehicle around, or to move a boom or to aim a nozzle. Even the guys on Mythbusters regularly convert cars and trucks to full remote control. See also Military robot, "Thermite" fire fighting unmanned ground vehicle, which could observe and could likely be modified to deploy a hose. Edison (talk) 14:53, 18 March 2011 (UTC)

Messenger Mercury orbiter

A new "MESSENGER" orbiter has just gone into orbit around Mercury. History shows the lifetime of Mercury landers is very short because of the high heat. How does the solar heating in Mercury orbit compare to that in Earth orbit? Mercury appears to have an average distance from the Sun of about 58 million km, (avg of aphelion and perihelion) compared to about 150 million km for Earth. Inverse square law would then suggest about 6.7 times the solar radiation intensity falling on a Mercury orbiter, than if it were in orbit around the Earth. An earth orbiter gets very hot on the Sun side and very cold on the other side, if not rotated. The Mercury orbiter has solar panels, so "barbecue mode" seems to be out. It looks like they have a white heat shield on the "back" of the instrument package, and a gold covered instrument package facing Mercury. Would the "Mercury shine" be a significant infrared heating source, leading to the designers not painting the non-sun side black for better heat radiation, with lots of surface area to radiate off heat? I realize that "space has no temperature," but things in space certainly do. Edison (talk) 17:15, 18 March 2011 (UTC)

"Mercury shine" is an issue: "The spacecraft’s orbit is elliptical rather than circular because the planet’s surface radiates back heat from the Sun. At an altitude of 124 miles, the re-radiated heat from the planet alone is four times the solar intensity at Earth. “By spending only a short portion of each orbit flying this close to the planet, the temperature of the spacecraft can be better regulated,” NASA documents explained."[22] Rmhermen (talk) 17:32, 18 March 2011 (UTC)

"MESSENGER will operate at room temperature behind a sunshade made of heat-resistant ceramic cloth."[23] but "the sunshade is made of Nextel™ AF-10 fabric[7], which not only can withstand extreme temperatures, but also has excellent thermal properties that limit the spacecraft’s temperature to below 140 C."[24] 140 C is a bit warmer than I keep my room! Rmhermen (talk) 17:42, 18 March 2011 (UTC)

Is that made out of crushed Nextel cell phones ? :-) StuRat (talk) 18:39, 18 March 2011 (UTC)

Operating the spacecraft close to the hot surface of mercury it is like opening an oven and looking into it. The temperature is only 250°C but your face gets hot. The sun is more like a normal light bulb at the same distance. The tungsten filament is 1500°C or more but the heat you get is much smaller. The spacecraft orbit is designed in a way that they heat up in close approach . (They have to do it on the day side because they want to take pictures). And than they go out into space to cool down. A lander was proposed landing at the day night boarder and slowly moving away from the sunrise, but upto now nobody dared to go to mercury to land. --Stone (talk) 19:16, 19 March 2011 (UTC)

Isn't the dark side of Mercury cool enough for a landing ? (I realize that Mercury doesn't have a permanent dark side, but I believe night is very long there, allowing a mission to complete in that time). StuRat (talk) 20:37, 19 March 2011 (UTC)

The dark side isn't cool, it's freezing cold. It can get down to nearly -200C. There is no atmosphere (or at least, no atmosphere worth mentioning - there is a little outgassing, etc.) so once you are out of direct sunlight, it gets very cold very quickly. The terminator (the day/night border) is the only place with reasonable temperatures for a long-lasting lander. --Tango (talk) 02:23, 20 March 2011 (UTC)

Tango, I don't think cold weather matters much at all for these probes unless we're at cryogenic levels. The problem is that Mercury is at a 3:2 (3 rotations per 2 revolutions) tidal-lock with the sun and has an orbital period of about 100 days. This means that the dark side of Mercury will become the scorching side after only 60 days, way too short for a science mission. SamuelRiv (talk) 05:25, 20 March 2011 (UTC)

60 days doesn't seem too short, to me. For an unmanned mission, the robot could explore, pick up some good samples, and leave with them, in that time. Alternatively, they could drill a hole and climb down inside to survive the heat when day comes. Or, for a second alternative, how about rolling towards the darkness continuously to increase the length of the mission while "seeing the sights". Let's see, at the equator Mercury has a semi-circumference of about 7665 km. Divide that by 60 days to get 128 km per day. If that's too much, land closer to either pole, to shorten it, as needed. Of course, a straight path may not work, since dangerous craters may be in the way, and that would need to be taken into account, too. StuRat (talk) 08:53, 20 March 2011 (UTC)

-200C is crygenic levels, isn't it? While those kind of temperatures aren't a problem in space, since you lose heat quite slowly in a vacuum, you wouldn't be able to maintain a reasonable temperature while in physical contact with rock at -200C. --Tango (talk) 20:46, 20 March 2011 (UTC)

Driving to stay ahead of sunrise? Ha! In seven years on Mars Opportunity has driven about 26 km. Opportunity's minimum operating temperature is -40 C (with heaters to keep it that warm), so -200 C is far below current spacecraft standards. Operating on the dark side of a planet requires an energy source other than solar. So it seems landing on the dark side is not reasonable at all. anonymous6494 21:57, 20 March 2011 (UTC)

Using nuclear bombs to generate power

I remember reading about a concept to use nuclear bombs detonated in a deep underground cavity to generate power. I can't remember what it's called though, does anyone know? There's an article on wikipedia about it... ScienceApe (talk) 19:39, 18 March 2011 (UTC)

Studying that was one of the objectives of Project Gnome. In a vaguely related vein, the Soviet Union's Nuclear Explosions for the National Economy programme included explosions designed to help the harvest of fossil fuels. -- Finlay McWalter ☻ Talk 19:51, 18 March 2011 (UTC)

I think what you want is PACER. --Mr.98 (talk) 20:02, 18 March 2011 (UTC)

Thanks. Does anyone know what the advantages/disadvantages of this would be compared to conventional reactors? Would this be safer?ScienceApe (talk) 01:35, 19 March 2011 (UTC)

It's terribly uneconomical, requires you to be constantly producing nuclear weapons, and while I'm not sure the risks have been fully worked out, they are certainly not non-existant, both from an exposure point of view and a theft point of view. It's the kind of thing that weapons designers think is a really great idea, but it is most certainly not the best way to do things. Keep in mind that to produce said weapons, you still have to run reactors or enrichment facilities anyway. --Mr.98 (talk) 02:40, 19 March 2011 (UTC)

I wonder how much is known about stress fatigue in large geologic formations. Wnt (talk) 21:28, 19 March 2011 (UTC)

Not only do you need enrichment facilities, you need much greater enrichment. For a bomb, you need about 90% U-235. For a reactor, 3% will do. (The starting point is 0.7%.) See Enriched uranium for details. I can imagine that using existing nuclear bombs to generate power as a way to make use of them while getting rid of them could be worthwhile (although even that seems unlikely to me), but creating bombs specifically for power generation is just ridiculous. --Tango (talk) 02:29, 20 March 2011 (UTC)

It would be interesting to calculate how much electricity would be used to enrich uranium for a bomb versus how much energy you could produce by blowing it up in a PACER scenario. Presumably these numbers are out there, somewhere. You might end up in the black if you did this — generating more energy than it takes to enrich. I don't know. (That still wouldn't make it a good idea.) --Mr.98 (talk) 17:23, 20 March 2011 (UTC)

I'm not sure what the energy requires for uranium enrichment are. It wouldn't surprise me if you would end up in the black. However, you would be far better off with a conventional nuclear reactor. --Tango (talk) 21:30, 20 March 2011 (UTC)

Evolution and sex

Male early humans were obviously more likely to use weapons and tools than female early humans. Tool usage selects for intelligence, dexterity, etc. To what extent will these traits be males, but not females? The reason I ask is that my friend tried to use this argument to "explain" why men were better than women (I think Darwin did the same)...the argument seems specious, but I don't know enough to rebuke it.

Also, more generally, when will the inheritance of some trait be sex-specific? 74.15.137.130 (talk) 20:09, 18 March 2011 (UTC)

Men only have one chromosome that women lack, the Y chromosome, so any difference between the sexes would have to lie there (or in lacking one of women's two X chromosomes). However, a "trigger" can exist there which turns on larger sections of any of the other chromosomes.

As for the argument, that would only make men better at use of weapons and tools. Women, on the other hand, seem to have developed superior communications skills and social intelligence, those being more important for living in a group while raising children. StuRat (talk) 20:23, 18 March 2011 (UTC)

I don't think it is obviously true that early human males were more likely to use tools than early human females. Assuming that the typical gender stereotypes hold (I'm not a paleosociologist, so I don't know how accurate this assumption is), men were probably more likely to use tools such as spears and axes, but women were probably more likely to use tools such as mortars and pestles and sewing needles. If anything, the smaller tools used by women might encourage more dexterity than the larger tools used by men. So it's not clear to me that the hypothesis has merit—it really requires better evidence and justification. —Bkell (talk) 20:33, 18 March 2011 (UTC)

I agree with StuRat. By default anything that changes in the human genome will affect men and women equally -- you have to add a dependence on sex hormones such as estrogen or testosterone in order to cause a feature to be sex-specific. Looie496 (talk) 20:52, 18 March 2011 (UTC)

There are many traits that are sex dependent. In fact, I remember reading somewhere that women are believed to have BETTER fine skills than men (for things such as weaving) while men are better at wider movements (For things such as throwing spears). If you ask my opinion, I don't believe it either way. Dauto (talk) 00:16, 19 March 2011 (UTC)

Yes, there are many traits that are sex dependent. But this is mainly because there are a large number of genes whose transcription is regulated, either directly or indirectly, by sex hormones. To get such regulation, though, there has to be a binding site in the DNA either for one of the hormones or for something regulated by one of the hormones; the default state is not to have such a binding site. Looie496 (talk) 00:34, 19 March 2011 (UTC)

I don't remember seeing anything like that in Darwin, and I frankly don't believe it. Darwin was one clever, perceptive writer. Wnt (talk) 23:03, 18 March 2011 (UTC)

http://en.wikipedia.org/wiki/The_descent_of_man#Part_II_and_III:_Sexual_selection

Yes, that sounds more like Social Darwinism, to me. StuRat (talk) 23:27, 18 March 2011 (UTC)

So, based on the comments, would it be safe to say that men using tools more frequently (if that was indeed the case) would likely benefit the species as a whole? 74.15.137.130 (talk) 01:39, 19 March 2011 (UTC)

Both men and women used tools. They may have used different tools for different jobs, but the use of tools has been a human trait for a very long time. As for the gender difference commonly cited in hunter-gatherer societies, it does not have to be genetic. Humans were smart enough to know that if a man dies, it doesn't have a large effect on the ability of the group to have children. If a woman dies, that reduces the number of children that can be born. So, men were tasked with risking their life for the betterment of the group while women were kept in relative safety. Because children must be safe also, it meant that women were kept with children while men went out to see if they would be lucky enough to return home. Of course, it could be a combination of genetic difference and social knowledge about child-birthing. Very few things are clearly one thing or another. Most things are a combination of causes. -- kainaw™ 04:31, 19 March 2011 (UTC)

Then why do female lions do the hunting? 74.15.137.130 (talk) 04:38, 19 March 2011 (UTC)

Compare the number of lions who die while hunting to the number of humans who died back when they were trying to take down large game with rocks and sticks. It is not comparable. You may as well argue "Then why do worms crawl underground?" as it is just as nonsensical. -- kainaw™ 17:08, 19 March 2011 (UTC)

Also interesting to consider perhaps: why do men have nipples? WikiDao ☯ 04:05, 19 March 2011 (UTC)

Earth going in a straight line while spacetime is curved

I read somewhere that objects under the influence of gravity (like the Earth) are actually travelling in straight lines while the massive object is bending spacetime. What is the meaning of "straight line" in this context? And how does one picture (or explain) this phenomenon? Thanks. 41.132.13.180 (talk) 20:46, 18 March 2011 (UTC)

General relativity says that objects move along geodesics; see that article for an explanation of why geodesics are considered "locally straight". Looie496 (talk) 20:49, 18 March 2011 (UTC)

I just think of that as a way to describe it, not that the objects really do travel in straight lines. StuRat (talk) 21:55, 18 March 2011 (UTC)

As Looie explained above, objects follow a geodesic which is the equivalent of a straight line for a curved space. For instance, if I say to somebody: "Follow a straight line due north and eventually you will get to the north pole", it is tacitly understood that a mean that person to stay on the earth's surface which means they are really not following a straight line because that would send them into space given that the surface of the earth is curved (curved space). I really mean that person to follow a geodesic and keep their feet on the ground. But in a sense their path is still straight. As straight as it can be without leaving the surface of the planet which is curved. Well, under the action of gravity objects follow a path that is as straight as it can be without leaving the universe which is curved by the action of gravity.

(EC) The Earth's world line is a "straight line" in the sense that it's as straight as possible, given that spacetime is curved. It's a straight line in the same sense that a line of latitude or longitude or a great circle on the Earth's surface is as straight as possible, given that the line is constrained to lie on the Earth's surface. However, it's important to note that the "straight line" that the Earth travels along is a line in a four-dimensional spacetime, in which straightness is measured using a pseudo-Riemannian metric, and is not a straight line in a three-dimensional Euclidean space. Three-dimensional Euclidean space does not physically exist, although Euclidean space can be used as a very good approximation in the common case of dealing with low speeds (compared to the speed of light) and little gravity. See also Geodesic (general relativity). Red Act (talk) 23:33, 18 March 2011 (UTC)

Thanks for your answers. I read the articles (as best I could!) and I have one follow up question. Let's say we collapse the the 3 space dimensions into 2 and then the time dimension is perpendicular to these two (ie pointing upwards) and look at this from the sun's perspective. So at t=0 the sun is at the origin and it goes straight upwards through time and the earth starts some distance away and moves in a helix so that at t= 1year it is back at the same point in space. My question is: does the mathematics say that this helix is a straight line? And what about the vertical line connecting the earths position at t=0 and t=1; is this also a straight line? 41.132.13.180 (talk) 10:39, 19 March 2011 (UTC)

Yes (the earth's orbit is a geodesic) and no (the "vertical" line is not a geodesic).

But -- and this is a rather large "but" -- your picture is not accurate. It is okay, so far as it goes, to remove one space dimension, but the result will not be the ordinary familiar 3-dimensional space you're picturing your helix in. The underlying four-dimensional space is curved, and the three-dimensional one you get by removing one dimension is still curved. If you squeeze it to make it fit into an Euclidean model, what used to be geodesics (such as the helix of the earth's orbit) will bend, but that is a product of your squeezing and doesn't say anything about the unsqueezed situation.

Also, the appropriate conversion factor between time and space is the speed of light, so the "vertical" height of one revolution in your helix would be one light year. That's huge compared to the earth-sun distance, so your helix does look extremely straight except in when you consider large times/distance (which is when the squeezing becomes relevant). –Henning Makholm (talk) 13:16, 19 March 2011 (UTC)

Here's an analogy. If you idealize the Earth as a sphere, a geodesic on the surface is a great circle. So let one person travel along the equator (which is a geodesic, i.e., "straight") and let another person set out at a slight angle to that, also in a "straight" line. Their paths will diverge at first, but they will start to converge a quarter of the way around the globe, and cross halfway around the globe, then diverge again until they start to reconverge 3/4 of the way around the globe... even though they're both traveling in straight lines. This is surprisingly close to what happens in general relativity. -- BenRG (talk) 20:27, 19 March 2011 (UTC)

transmutation of nitrogen

Since oxygen(8)has greater mass than nitrogen(7),how could Rutherford's transmutation of nitrogen into hydrogen and oxygen by iradiation have produced oxygen without a high temperature fusion event? Is fusion NOT always neccessary to produce a heavier element? Where does the extra proton come from?190.148.132.226 (talk) 21:25, 18 March 2011 (UTC)

Note that oxygen doesn't have to have a greater mass than nitrogen. It just has more protons than nitrogen. If you convert a neutron to a proton, you can increase the atomic number with no gain in mass (a slight loss, actually, at least on average). Wnt (talk) 22:57, 18 March 2011 (UTC)

For your specific instance, according to Ernest Rutherford, "In Cambridge in 1919, after taking over the Cavendish laboratory, Rutherford became the first person to transmute one element into another when he converted nitrogen into oxygen through the nuclear reaction ¹⁴N + α → ¹⁷O + p". Note that the alpha particle is a helium nucleus, making this a case of nuclear fusion. Wnt (talk) 23:01, 18 March 2011 (UTC)

Note also that the alpha particle was produced by some radioactive decay and had a lot of kinetic energy allowing the fusion to happen. Dauto (talk) 01:39, 19 March 2011 (UTC)

Safe energy?

Is any form of energy totally safe when improperly handled? Which is the safest (in the broadest sense) form of energy for human use? --78.150.226.145 (talk) 21:44, 18 March 2011 (UTC)

If you mean source of energy, there are plenty, such as solar and wind, but they have other disadvantages, like not always being available.

If you mean ways to store energy, then probably not, if they store large amounts. This implies unstable chemical or nuclear bonds (otherwise you would need to use more energy to break those bonds than you would get from them, once broken), which can then catch fire and/or explode, like wood, gasoline or hydrogen gas. StuRat (talk) 21:49, 18 March 2011 (UTC)

No, the whole point of energy is that it has energy, and if you handle it in such a way that the energy is released uncontrolled it causes damage. The safest in the broadest sense is nuclear power. By far. It releases the least amount of waste, and has killed the fewest people. (Adjusting by amount of energy produced from that type of energy of course.) Ariel. (talk) 21:51, 18 March 2011 (UTC)

In declaring nuclear power's safety, I doubt that you have factored in future deaths from exposure to poorly managed nuclear waste. HiLo48 (talk) 22:29, 18 March 2011 (UTC)

We haven't had any in 60 years (from waste, poorly managed or not), and I have no crystal ball. Have you factored in future deaths from pollution generated by other forms of energy? Ariel. (talk) 22:52, 18 March 2011 (UTC)

Haven't had any? I'd love to see proof of that. And anyway, 60 years is a tiny fraction of the period for which this stuff remains dangerous. Given world political history for the past thousand years, can you tell me with certainty who will be managing India's nuclear waste in a thousand years time? HiLo48 (talk) 22:59, 18 March 2011 (UTC)

You're asking me to prove a negative? And given the world political history for the past thousand years it will be the human descendants of the current generation who will be managing the stuff. And they will be highly technical. Sorry, but I don't believe in theories that think humans will "go down". Historically it may happen at a regional level, but it has never happened globally, and as long as a reasonably sized group exists anywhere in the world, dangerous places like waste sites will be managed. (PS. I will not be able to reply to replies for a day of so.) Ariel. (talk) 23:16, 18 March 2011 (UTC)

You made the negative claim as a point on your side of the debate, so of course I'm asking you to prove a negative. And yes, problems will occur at a regional level. That's why my question was explicitly regional. Most of your argument seems to be based on faith that we can mange a very complex science. HiLo48 (talk) 23:22, 18 March 2011 (UTC)

For nuclear waste-related illnesses/death, see Mayak. While tracing any individual death to waste exposure is hard, the odds are very high that waste exposure there has led to quite a number of deaths amongst workers and those living in the area. It's probably the most polluted place in the world from a radiological point of view. I don't think it's indicative of how radioactive waste hazards have to be — they were exceptionally poorly managed there, by a government that cared not at all what happened to the people who lived there — but it certainly is indicative of what happens if you don't try to be responsible about it. Let's not forget that we're not just talking about the US and Europe here. --Mr.98 (talk) 00:45, 19 March 2011 (UTC)

Excluding renewable sources like solar and wind, presumably? They haven't killed anyone to my knowledge! Regards, --—Cyclonenim | Chat  21:59, 18 March 2011 (UTC)

During BBC Radio 4's prestigious political debate programme Any Questions? yesterday, panellist Toby Young stated (and was not challenged by fellow panellists environmental lobbyist Jonathon Porritt, Minister of State for Energy and Climate Change Greg Barker, or Shadow Health Secretary Diane Abbott) that over the last 10 years the Nuclear industry had averaged 7 worker deaths per year, while the Wind Energy industry had averaged 44 deaths per year. {The poster formerly known as 87.81.230.195} 90.197.66.165 (talk) 02:23, 19 March 2011 (UTC)

And presumably also excluding the people who died from political infighting over control of uranium supplies, or in mining accidents, or mining-related illnesses. --Stephan Schulz (talk) 22:05, 18 March 2011 (UTC)

Who died from infighting over control of uranium supplies? --Mr.98 (talk) 00:46, 19 March 2011 (UTC)

I would be very cautious about raw, unqualified figures like these. Over what time period? Over what geographical area UK, Europe, worldwide? How do the number of employees in the industries compare? Richard Avery (talk) 08:21, 19 March 2011 (UTC)

Solar and wind have not generated enough energy to count (over the last 50 years or so). And I did include mining accidents - on the plus side for nuclear power, since all other forms of energy require much more mining. And has there really been that much infighting for control of uranium supplies? Ariel. (talk) 22:52, 18 March 2011 (UTC)

The safest energy source is conservation. The next safest is investments in efficiency, but perhaps I'm just confused because "tax cuts" have been renamed "tax expenditures". Hcobb (talk) 22:15, 18 March 2011 (UTC)

Conservation isn't an energy source, it's an energy-saving proposition. Investing in efficiency isn't an energy source either. Regards, --—Cyclonenim | Chat  22:20, 18 March 2011 (UTC)

Nuclear energy chain is the safest form of energy production world-wide, but in the EU hydroelectricity is yet safer (ref). Comparison of "safety" is hard because standards vary accross the globe, nuclear might be safer because the West has large reserves of uranium. --85.77.98.144 (talk) 14:24, 19 March 2011 (UTC)

Leg injury

Hey all! I'm writing a short story for a composition class and I want it to at least make sense on the surface. Are there any leg muscle injuries that one could sustain that would prohibit the riding of a bicycle but that would not be noticed or impede with other activities such as walking, jumping, or climbing stairs (etc)? Thank you. 72.128.95.0 (talk) 22:48, 18 March 2011 (UTC)

Not that I can think of. How about an injury to the buttocks that makes sitting painful ? StuRat (talk) 22:53, 18 March 2011 (UTC)

I don't think there is any leg injury that has zero effect on walking, but it's pretty easy to get a knee injury that makes riding a bike impossible but has only a minor effect on walking, because of the much greater bending of the knee required for bicycling. Injuries of that type also make climbing stairs a problem, though -- at least in my experience. A strain of the gluteus maximus can also have a larger effect on bicycling than on walking -- but it will also making rising from a chair painful. Looie496 (talk) 00:00, 19 March 2011 (UTC)

Bruising of the soft tissues covering the medial surface of the inferior ramus of the ischium often makes it difficult to ride a bike, but has little effect on walking. -- Scray (talk) 02:44, 19 March 2011 (UTC)

Would painting your pool bottom and sides black made the water any warmer?

Just a random thought. Topic says it all. I can't recall ever seeing a pool that wasn't white-bottomed, though I suspect this is more to aid in cleaning than anything else. The Masked Booby (talk) 23:02, 18 March 2011 (UTC)

Yes, it would make the water slightly warmer. I think the reason for white pools is that they are safer, since you can see when you're about to hit bottom or the side. In a black pool people would also run into each other, as there would be less reflected light for them to see each other. StuRat (talk) 23:30, 18 March 2011 (UTC)

If you do a Google Image search for "black bottom pool," you can see examples of this. Some people prefer it. I have swam in such a thing. --Mr.98 (talk) 01:34, 19 March 2011 (UTC)

I'm not sure why people would RUN in a swimming pool but certainly many HAVE SWUM in one. Cuddlyable3 (talk) 11:55, 19 March 2011 (UTC)

run into: (intransitive but with prepositional object) To collide with / To cause to collide with. Perfectly correct use of the term by StuRat; it does not have to mean literal running took place (as many who have ran their cars into various things know). The only thing worse than a pedant is an incorrect pedant. --Mr.98 (talk) 13:58, 19 March 2011 (UTC)

While we're on the subject of pedantry (aka knowledge of basic English), it should be "have run their cars". 86.183.1.249 (talk) 14:47, 19 March 2011 (UTC)

Indeed. See List of English irregular verbs. Cuddlyable3 (talk) 01:35, 20 March 2011 (UTC)

cudnt help laughingg out loud, you guys are indeed pedantic :)))--Fragrantforever 05:16, 20 March 2011 (UTC) — Preceding unsigned comment added by Fragrantforever (talk • contribs)

According to this black-bottom pool enthusiast, the black bottom is used more for a classy "mirror" effect. My guess is that the water looks more mirrored because there is much more contrast when looking at a reflection of a colored object on it, but it does make me wonder if the diffraction in water might cause a different effect with a black bottom? I am reminded, however, of the solar oven. SamuelRiv (talk) 05:32, 20 March 2011 (UTC)

March 19

car

what brand car is in this vid http://www.youtube.com/watch?v=4vS4U1xXQwQ — Preceding unsigned comment added by Wdk789 (talk • contribs) 02:00, 19 March 2011 (UTC)

This is a video clip running for 3 minutes and 10 seconds. It shows a very un-funny prank in numerous fast-food driveways. The car is entirely irrelevant to the prank. You can't see enough of the car to determine its brand. I suggest no-one even bothers to download the video or watch it. Life is short enough as it is without wasting a few minutes on boring stuff like this. Dolphin (t) 04:25, 19 March 2011 (UTC)

It is pretty funny. At points it sounds like this. Bus stop (talk) 01:54, 20 March 2011 (UTC)

lights

how do they change the head lights in this http://img.ibtimes.com/www/data/images/full/2011/03/17/75371-dd.jpg — Preceding unsigned comment added by Wdk789 (talk • contribs) 04:26, 19 March 2011 (UTC)

This is just a link to a photograph of spent fuel rods at the bottom of a pool of water in a nuclear reactor. There is no car, or any other vehicle, visible in the photograph so there are no head lights. Don't bother. Instead, spend the time checking out the contributions from Wdk789. Dolphin (t) 04:31, 19 March 2011 (UTC)

Perhaps he meant to ask how they change the lights in the radioactive areas of a nuclear plant, and mistakenly called them "headlights" ? StuRat (talk) 17:22, 19 March 2011 (UTC)

yes— Preceding unsigned comment added by Wdk789 (talk • contribs) 22:06, 19 March 2011

The glow on that reactor, though, is Cherenkov Radiation and a natural effect in the air above energetic particles flying about. Whatever additional lights are used are probably fluorescent tubes energized also by the reactions themselves, thus not needing to be changed. Of course, the nature of such a reactor design is such that it's actually safe to walk around it with an open top. SamuelRiv (talk) 05:34, 20 March 2011 (UTC)

Liver question

What is difference between compensatory hyperplasia and regenration of liver? —Preceding unsigned comment added by 210.2.181.244 (talk) 07:47, 19 March 2011 (UTC)

Does bicarb remove the acidity of acetic acid (apple cider vinegar)?

Can I just confirm that adding any amount of bicarbonate of soda would lower the acidity affects of vinegar (acetic acid)? The fact that bicarb is an 'amphoteric' (react as an acid as well as a base) doesn't clarify whether it would make vinegar more effective or less? 220.244.35.181 (talk) 09:43, 19 March 2011 (UTC)

It reduces the acidity of acids, because it acts like a base when in contact with acids. Grandiose (me, talk, contribs) 10:40, 19 March 2011 (UTC)

Thanks! you know what's also interesting and confusing, is that there is a formula for getting rid of mould/mildew in showers - and it instructs that you mix white vinegar with bicarb: the vinegar is to kill the mildew and the bicarb is to eliminate the odour of the vinegar - but how would that work if the two cancel eachother out???

220.244.35.181 (talk) 10:49, 19 March 2011 (UTC)

It confuses me too, when the ingredients are mixed, they no longer act as two substances with distinct properties. The new substance produced, is a solution of sodium acetate with completely different properties. Plasmic Physics (talk) 11:15, 19 March 2011 (UTC)

that's simplistic. vinegar + bicarbonate forms a buffer solution at some fixed pH (so long as there is not an overwhelming amount of either the vinegar or the bicarbonate.). This pH is still acidic enough to kill unprotected mildew. The free acid CH3COOH is what is smelling like vinegar (vinegar is volatile and evaporates). That's because it's at a considerably low pH (vinegar has around a pH of ~2.4) so there's a lot of free acid. A buffer solution of sodium acetate and acetic acid I believe, has a pH of around 4.76. That's still acidic enough to hinder growth, but not that acidic. Also, the acetate ions help sequester the free acid RCOOH molecules from evaporating. 199.111.169.216 (talk) 16:34, 19 March 2011 (UTC)

Just remember that mixing the two gives you a nice release of CO2, making it ooze bubbly foamy stuff. Fun thing to show your kids. SamuelRiv (talk) 05:36, 20 March 2011 (UTC)

• OP here. Thanks for the help. Then it's confirmed, I won't be mixing any bicarb with the vinegar because we want a lower pH level. Thanks 220.244.35.181 (talk)

What does the atmospheric pressure of CO2 have to be for the dominant equilibrium to be: carbonic acid + acetate <------ -----> acetic acid + bicarbonate? 199.111.185.182 (talk) 16:40, 20 March 2011 (UTC)

Identifying an actual triquetral bone

Triquetral is marked "D"

On File:RightHumanAnteriorDistalRadiusUlnaCarpals.jpg and File:RightHumanPosteriorDistalRadiusUlnaCarpals.jpg, which bone is the triquetral? I've left an image note on the anterior image for what I think is the triquetral, but I can't be sure, and I don't think it's visible in the posterior image. Nyttend (talk) 12:00, 19 March 2011 (UTC)

According to the article triquetral bone, it is the triangular bone marked C, not D. See the summary notes here.. Cuddlyable3 (talk) 13:50, 19 March 2011 (UTC)

According to Gray's Anatomy here the small bone marked 'D' is the pisiform and the other bone, 'C', is called the triangular or os triquetrum. Richard Avery (talk) 14:46, 19 March 2011 (UTC)

So I marked the bone labelled D? I know that it's C — my problem is that I can't easily figure out which bones in the diagram correspond to which bones in the photograph. If I marked the wrong one, would you please remove the note and place it on the correct bone? Nyttend (talk) 17:43, 19 March 2011 (UTC)

Oh, I just realised that I gave the wrong caption to the image here. Sorry — that was a typo, and I meant to say "C" on the caption. Nyttend (talk) 17:55, 19 March 2011 (UTC)

Which is this?

Video. Is this a MiG-23 or a MiG-27? 1:16 in the video or so is probably the best image. These are very similar aircraft, so maybe we can't tell. SDY (talk) 13:53, 19 March 2011 (UTC)

Libyan air force#Current air force equipment says "On 19 March 2011, the rebels shot down one of their captured MiG-23BN over Benghazi", but only sites as a reference that same video, which doesn't explicitly make that identification. -- Finlay McWalter ☻ Talk 14:00, 19 March 2011 (UTC)

Agenzia Giornalistica Italia identifies it as a MiG-23 (but doesn't specify which type) here, but the Sydney Morning Herald says it was later identified as a Mirage here. -- Finlay McWalter ☻ Talk 14:20, 19 March 2011 (UTC)

Sky News also claims it's a MiG-23 here. -- Finlay McWalter ☻ Talk 14:25, 19 March 2011 (UTC)

It can't be a Mirage, the planform is completely wrong. SDY (talk) 14:37, 19 March 2011 (UTC)

Matter to energy

If matter is converted to energy, and the matter happens to be in a gravitational field, then what happens to the matter's gravitational potential energy? —Preceding unsigned comment added by 86.183.1.249 (talk) 14:36, 19 March 2011 (UTC)

See gravitational redshift. Icek (talk) 15:29, 19 March 2011 (UTC)

Matter is NOT converted to energy. Matter IS a form of energy. When matter is converted to a different form of energy its potential energy remains there because the new form of energy still possesses a relativistic mass given by the famous formula E=mc² identical to the mass that the matter had before. Dauto (talk) 16:07, 19 March 2011 (UTC)

Is this connected to the fact that an object weighs more when it is heated? The gravitational potential of the heat energy is manifested as extra weight? 86.160.211.135 (talk) 18:47, 19 March 2011 (UTC)

Yes, that's it. Any form of energy has a mass given by E=mc². Dauto (talk) 19:29, 19 March 2011 (UTC)

Thanks for your help. 86.160.211.135 (talk) 20:05, 19 March 2011 (UTC)

Aquatic minibeasts

Okay, this is a long shot. What minibeasts might I have seen in a sunny ditch in Oxfordshire? The ditch was calm and a sort of temporary (but recurring) pond in the middle of a field. It still had alive-looking grass at the bottom. There were a few minibeasts that looked like pale mites or ticks, gliding through the water, but the ones I'm most interested in were there in large numbers, and looked like small ants although I didn't see legs. They were reddish-brown and moved constantly in a jerking motion: their movement was made up of lots of little straight-line pushes, a bit like Brownian motion but with acceleration that looked like little repeated pushing glides. Perhaps they move by releasing something suddenly behind them?

I'm aware this may not be possible without a picture, but I appreciate any information. 212.183.128.107 (talk) 15:03, 19 March 2011 (UTC)

I'm not sure about jet-type propulsion, but at that size class*, a high density critter in an ephemeral pool is likely an aquatic insect larva. See a visual overview of shapes here [25]. Did they look at all like mosquito larvae? Some sort of Dipteran larvae would be my guess with such limited info. *I assume 'small ant' size is ~1-2mm. SemanticMantis (talk) 16:50, 19 March 2011 (UTC)

Another guess which fits with "moved constantly in a jerking motion" is Daphnia which are very common even in quite small pools in the UK. Country folk call them "water fleas". Mosquito larvae tend to wriggle and it may be too early in the year for them. Another slightly smaller relative is the Cyclops. They both have a little pair of arms with which they do a sort of butterfly stroke - hence the jerking action. The best thing is to fish some out in a jam jar next time you're passing and have a look with an ordinary magnifying glass. This page is a simple key to pond invertibrates; click on the drawing for more details. This page is more comprehensive, but not so easy-peasy. Alansplodge (talk) 19:50, 19 March 2011 (UTC)

Me again. Looking at the naturegrid.org.uk page linked above, it says that "Daphnia contain haemoglobin - which is also found in human blood. This substance can hold and process a lot of oxygen. It turns red when it contains oxygen." That fits with the reddish-brown colour that you reported. Alansplodge (talk) 20:16, 19 March 2011 (UTC)

Thanks (I'm the OP), this is all really good. I agree that a jamjar and magnifying glass would make this a lot easier: I might be able to try that in a couple of days. I was pretty sure they weren't mosquito larvae, partly because it seems too early, but also because I first went to look closer because of the sparkles on the water: I wanted to see if it was air bubbles or little creatures like mosquito larvae. And these weren't doing the tube-to-the-surface thing that mosquito larvae do (unless they don't always do that: I shall look it up). I didn't think they were water flea or triops/cyclops shape, although maybe the angle they are in the water makes them look different. 86.164.66.59 (talk) 23:25, 19 March 2011 (UTC)

Daphnia are roughly disc-shaped, so viewed from above they would look different to the linked photos which all show the side view. However it may well be something else; I'm an amateur at pond-dipping. Good hunting! Alansplodge (talk) 01:51, 20 March 2011 (UTC)

Ocular dominance vs. amblyopia

If one cannot read (discern letters) with his left eye when the right eye is closed, is this an ocular dominance or rather amblyopia?--89.76.224.253 (talk) 16:01, 19 March 2011 (UTC)

It isn't either one of those things. Ocular dominance and amblyopia are both conditions in which one eye dominates the other when both are open -- neither says anything about what happens when one eye is closed. See ocular dominance and amblyopia for more information. Looie496 (talk) 18:20, 19 March 2011 (UTC)

Um, let me correct that. Amblyopia is a condition in which one of the two eyes sees poorly in an absolute sense -- but there are many conditions other than amblyopia that can cause one of the two eyes to see poorly. Looie496 (talk) 20:08, 19 March 2011 (UTC)

I recently spent some time reading about various eye conditions. Lazy eye seems to present in a way that it can be observed by other people (check google for images). Eye dominance is natural preference of one eye over another (muck like beeing right or left handed). What you describe might as well be something else (say, a refraction error in left eye) ~~Xil (talk) 10:07, 20 March 2011 (UTC)

Identifying the contents of a 55-gallon drum by the torn remnants of its MSDS

During a recent binge of idiocy my friend decided 55-gallon drums would make awesome trash bins. Except he didn't want to buy them new, so he dumpster-dived a few. The several we already have work fine (as their MSDSes were intact and didn't show anything freaky)... but one of them is kind of worrying. This particular black plastic 55-gallon drum was discarded by a now-defunct steel and wire processing company and most of the attached MSDS was destroyed by the elements. From what we can read though it's kind of awful, so I really want to know what's on the rest of the MSDS. I know there are different categories of danger based on the wording of the sentence (i.e. "may be harmful if ingested" and "harmful if ingested" and "toxic if ingested" and "poisonous if ingested" denote totally different levels of toxicity). So can anyone get an idea of what this crap is (or give me tips as to doing the same) based on this meager information? (Words that have worn off replaced with #)

On the barrel itself was a stamped sequence of numbers "USA/R-1608/RL/03/10".

SKIN CONTACT
Remove contaminated clothing. Wash affected #### with soap and water for at least 15 minutes #### medical attention of irritation persists.
EYE CONTACT
Remove contact lenses. Hold eyelids apart and flush with plenty of water for at least 15 minutes. Seek immediate medical attention if irritation persists.
INHALATION
Remove victim to fresh air. Restore breathing if necessary. Seek medical attention if irritation persists.
INGESTION
Seek prompt medical attention. Do NOT induce vomiting. Never give anything by mouth to an unconscious person.
########
########
## be harmful if swallowed. May cause mild to severe eye irritation upon prolonged, repeated exposures. Prolonged or repeated exposure may cause skin ### defatting and irritation ranging from mild to severe. May cause mild to severe respiratory irritation with repeated, prolonged exposures.
See MATERIAL SAFETY DATA SHEET for additional health-related information.
OTHER PRECAUTIONS
Use all personal protective equipment. Observe good personal hygiene practices, such as washing after handling and before eating, drinking and/or smoking.
KEEP OUT OF REACH OF CHILDREN
##################
##################
appl##############
enter s###########
has enter#########
exte##############
WASTE ############
Uncontaminated ###
tim### Recyclin###
disposal. Foll####
H#################
Keep from freezing. Store######
area away from all ignition s##
incompatibles. Keep containe###
MSDS Rev No. 01 MSDS Date: 03/12/10

I'm thinking of just googling the longest intact segments or running them through a MSDS search engine, but anything else that works better would be a hell of a great help. ZigSaw 20:41, 19 March 2011 (UTC)

One hopes R-1608 might be a product number (no guarantees). But isn't there a company name on the barrel (not the wire company that bought it, but the manufacturer)? Wnt (talk) 21:23, 19 March 2011 (UTC)

Let's just hope he doesn't find the number 311-555-8674 stenciled on it. ;) Wnt (talk) 21:26, 19 March 2011 (UTC)

You've forgotten to put the thing canvcelling the small type. 92.24.178.214 (talk) 23:23, 19 March 2011 (UTC)

R-1608 is one of the names for an herbicide more commonly known as EPTC or eptam. It appears to have toxicity data similar to that on the label. Looie496 (talk) 23:26, 19 March 2011 (UTC)

The points listed above are on just about every MSDS ever made. I would suggest looking for a different drum. Or at least rinse it out and line the drum with a couple garbage bags to keep a barrier between your nice new garbage and whatever was originally in it. 50.92.121.76 (talk) 22:39, 20 March 2011 (UTC)

Humans from Africa

When humans spread out from Africa, were there already some human-like creatures (such as Neandertals and others) in the land they expanded into? Thanks 92.24.178.214 (talk) 23:20, 19 March 2011 (UTC)

The answer is yes. Just be careful to define what you mean by human. Neanderthals may also be considered human depending on your definition. Dauto (talk) 23:39, 19 March 2011 (UTC)

The article Early human migrations will get you started on this question, and you may find further relevant details by following links from it. You will also find a useful table of the different known Human/Homo species in the Homo article, and further details towards the end of Timeline of human evolution.

Briefly, when the only (known) now-surviving human subspecies Homo sapiens sapiens first spread beyond Africa (though many stayed there), there were likely still some closely related sub-species in Africa such as Homo sapiens idaltu, perhaps also some of the last Homo antecessor and/or Homo heidelbergensis whose earlier emigrants to Europe had evolved into Neanderthals, and possibly some surviving Homo ergaster (aka "African erectus") from whom H sapiens had evolved (also via H antecessor and heidelbergensis), and Homo rhodesiensis.

(Remember, when one species evolves "from" another, it often does so in one particular locality because of special conditions there, leaving populations of the first species still continuing to live elsewhere, from whom further species may subsequently evolve - there is not necessarily a strict line of succession and immediate replacement.)

Beyond Africa there were already: the species/subspecies Homo neanderthalensis/Homo sapiens neanderthalensis in the Levant and Europe (with whom H sapiens sapiens then interbred); Homo denisovan (or H sapiens denisovan?) in parts of Eurasia, (with whom some H sapiens sapiens also interbred); Homo erectus (divided into several localised sub-species) throughout Eurasia, Indonesia and possibly parts of Australasia (with whom H s s probably did not interbreed - though see Homo erectus soloensis - and whom we replaced), and Homo floresiensis (perhaps a descendant from erectus, perhaps from an Australopithecus species, perhaps something else - the jury is still out) in Flores and perhaps elsewhere.

There may well have been other localised Homo species and subspecies that we have not yet discovered. Several of the above-mentioned varieties of humans are known only from very few fossils, so future finds may well extend their currently confirmed time spans nearer to the present day. {The poster formerly known as 87.81.230.195} 90.197.66.165 (talk) 01:24, 20 March 2011 (UTC)

March 20

What would it take to invent a vacuum-operated toilet?

If we don't have enough time in the day to even answer the call of nature the normal way, could there be a vacuum toilet that sucks out all the bodily wastes so that we wouldn't have to spend as much effort pushing it out ourselves? How much faster could this process be if this was vacuum assisted? Would it do a better job than normal? Would it be able to suck out more waste than we can push out?

So how come there hasn't been a vacuum-operated toilet yet? --70.179.169.115 (talk) 02:33, 20 March 2011 (UTC)

Astronauts use something similar, but you don't want so much suction that it can do damage. A minimal vacuum, just to suck the stench out, might work. StuRat (talk) 02:40, 20 March 2011 (UTC)

Before anyone goes through the effort, can you show that it's even necessary? Who says that we don't have enough time in the day to go the normal way? Dismas|^(talk) 03:08, 20 March 2011 (UTC)

It wouldn't work as you expect. To avoid disgusting mental images, think of this scenario: You have a plastic bag full of liquid. It has a narrow rubber hose so the liquid can drip out. To get it out, you squeeze the bag. That is how it should work. To make it faster, you suck the liquid out. The result is that the rubber hose collapses. Sucking harder makes the rubber hose squeeze tight. Nothing come out. The solution is to shove a stiff straw up the rubber hose to keep it from collapsing. Then, you have no problem sucking the liquid out (that's how those juice bags that kids drink work - they use a hard straw, not a flimsy little tube). So, your vacuum would actual keep you from evacuating your bladder or bowels instead of making it faster. The solution would be a stiff tube shoved in one hole or the other before attaching the vacuum - which will likely take longer than just going to the bathroom. So, what do people do? That's why they make magazine racks for bathrooms. Some people have televisions in their bathroom. Whatever you need to do, find something that allows you to sit for a while. -- kainaw™ 04:16, 20 March 2011 (UTC)

Well then Kainaw, I guess I'll have to resort to a liquid-based "straw" called the Washlet. I wonder if that's what they have in the space stations. --70.179.169.115 (talk) 08:09, 20 March 2011 (UTC)

Read Packing for Mars by Mary Roach; she discusses this stuff in enjoyable detail. --jpgordon^{::==( o )} 04:56, 20 March 2011 (UTC)

Death of Abigail Taylor tells me that no one should ever attempt sucking his or her butt. If the issue is that you just don`t want to go to bathroom, you might try catheter (not sure if it would work for moving bowels though) ~~Xil (talk) 10:48, 20 March 2011 (UTC)

If you are concerned about the time and effort involved in voiding waste, those are both related to diet, notably dietary fiber intake. SemanticMantis (talk) 14:22, 20 March 2011 (UTC)

I agree, if you have this problem, then its a sign that you should be eating more vegetables fruit and wholemeal grains. 92.15.21.23 (talk) 23:08, 20 March 2011 (UTC)

I think they already exist, front side anyway. Fighter pilots like these http://www.bbc.co.uk/news/uk-12798613 have white tubes as part of their jumpsuit. On an eight-hour trip they are going to need one. Perhaps they are required to have an enema before leaving too. 92.28.241.202 (talk) 15:52, 20 March 2011 (UTC)

But note that any vacuum used in such suits is low, only sufficient to remove the waste once voided, not to actually pull it out of the body. StuRat (talk) 19:23, 20 March 2011 (UTC)

Likewise for the ones astronauts use. The vacuums in "space toilets" just replace gravity, they don't replace the body's own forces. --Tango (talk) 21:35, 20 March 2011 (UTC)

How do Tomahawk missiles get to the target without getting shot down?

The Tomahawk cruse missile was used in several recent conflicts against countries with late Soviet air defense systems. They apparently reached their targets without interference, even before radar, antiaircraft defense, and fighter jets were incapacitated. The Tomahawk is a jet powered drone rather than a ballistic missile or rocket. The WW2 V1 flying bomb flew along at 400 mph, and WW propeller fighters could sometimes shoot them down, even with the primitive radar of the time. The Tomahawk only flies at 550 mph, comparable to a commercial airliner, and a fraction of the speed of even the old Mig and Mirage fighters operated by such countries as Iraq and Libya. Flying at low level to avoid radar was a common practice even in WW2, and did not really protect bombers from detection and damage. The ability to fly at 100 feet through canyons or whatever would not help while they are still out over the Mediterranean, where fighters might be deployed as a defense. Do second rate air defenses like Libya rely on ground based radar, and have nothing comparable to Awacs to "look down" and detect the Tomahawk in tome to fire a ground to air or air to air missile at one? Do the best Libyan fighter planes have "look down, shoot down" systems? Would a first rate world power be able to detect and shoot down Tomahawk quality missiles? This report from the Gulf War claims that only 60% of the Tomahawks actually hit their targets. Were some of the "misses" actually shootdowns? Edison (talk) 03:12, 20 March 2011 (UTC)

They are sometimes shot down. This PBS page says that as many as 6 were shot down in the Gulf War (out of 297 fired). It also lists counts for many other reasons they didn't reach the target. The point of the Tomahawk is that it is cheap and dependable (and what they blow up costs a lot more than a few Tomahawk missiles). -- kainaw™ 04:10, 20 March 2011 (UTC)

Cheap and dependable? The things cost $569,000 each in 1999 dollars,[26] which for a single-use weapon makes "cheap" a stretch. And according to the source cited by Edison, more than 40% of the time Tomahawks don't hit their intended target (often blowing up innocent civilians instead), which makes "dependable" a stretch. Red Act (talk) 09:39, 20 March 2011 (UTC)

Cheap depends on context. If the alternative is even a 1% chance that your billion dollar bomber is shot down, then a cruise missile would look cheap. Dragons flight (talk) 11:12, 20 March 2011 (UTC)

Is that really how much one of those missiles cost? I would have guessed a much higher price in the range of several million dollars. I think that's a relatively cheap price tag. Dauto (talk) 14:21, 20 March 2011 (UTC)

I think you've identified some of the deficiencies in third rate militaries. Another big one is the lack of communication between systems. You need the radar systems (ground, sea, air, and satellite), to all be hooked to each other, so they can identify a "bogey", track it, and fire a missile at it when it comes into range. Even if you have all the components, if they aren't connected properly, it's just about useless. StuRat (talk) 08:37, 20 March 2011 (UTC)

News media sometimes give the impression that when a destroyer or sub fires one of these things at a country, the target is doomed, but I still haven't seen arguments as to whether a country such as India, Pakistan, or the UK or US, for that matter could spot and intercept one or more fired, say from a submarine a hundred km offshore. If they are following a canyon or flying between hill, a few might be expected to hit those geographic features or even powerlines, and skimming treetops and wavetops was certainly a WW2 tactic. Radar at 30,000 feet looking down should spot it better than ground based radar, and jet fighters for the past several decades have flown much faster than these devices. If everything works right, the GPS should let the launching country put 1000 pounds of high explosive close enough to a target to blow it up, at about a million dollars per explosion, but I wonder if it has a positional uncertainty in tens or hundreds of meters, making it less effective against hardened targets than laser guided bombs, which (at least in selected footage from the attacks on Iraq) could be flown right in a window. They tend to use about 5 Tomahawks per target. Edison (talk) 20:13, 20 March 2011 (UTC)

Then there's the additional problem that the Israelis had when using the US-built Patriot missile, during the Gulf War, to shoot down Iraqi SCUDs. The SCUDs were inaccurate, and carried minimal warheads, meaning they weren't likely to create much damage when they hit. Shooting them down meant that both the remnants of the SCUD and the Patriot would then fall, frequently in a populated region, causing as much damage as the intact SCUD would have. StuRat (talk) 20:50, 20 March 2011 (UTC)

There is a significant difference in the consequences of shooting down a low flying cruise missile and that of shooting down a ballistic missile during its terminal phase. -- 119.31.121.89 (talk) 23:02, 20 March 2011 (UTC)

Not a conspiracy theory question but a true scientific question

Was reading about the conspiracy theories floating around about the Earthquake and Tsunami in Japan. This is not a political or a conspiracy theory question, neither is it in any way intended to insult the suffering people now. I would like to know, is it possible( does technology exist) to artificially create earthquakes at an intended site and plan a tsunami? Whats the science behind this, how does this work?--Fragrantforever 05:13, 20 March 2011 (UTC) — Preceding unsigned comment added by Fragrantforever (talk • contribs)

No, it is not possible for mankind to create earthquakes or tsunamis. The technology does not exist. The technology does exist to pinpoint the epicentre of any earthquake, and it is now known that earthquakes occur many kilometres below the Earth's surface. This is a depth at which mankind has never had any influence. Also, the energy involved in an earthquake is truly immense. It makes manmade sources of energy look miniscule.

Psychology is the science of behavior. This science does exist. It is known that when people are deeply distressed they display a range of emotions (anger etc) not normally seen in people who are free from distress. Some of these emotions are demonstrably irrational, and can be of extreme intensity. One of the characteristics of anger is the ability to display antipathy towards another person, or other people. When people are angry they often display a readiness to accept suggestions and rumors about how another person has, or other people have, deliberately brought about the event that caused the deep distress in the first place. For example, during a war people have displayed a naive readiness to accept suggestions and rumors that the enemy is extremely bad and wants to cause extreme suffering and hardship. After the war, these suggestions and rumors have usually been found to have no foundation. Similarly, in the aftermath of an accident the victims often display a naive readiness to target a person or group of people, and to believe that the accident was either deliberate or solely due to the criminal negligence of this person or group of people.

With this in mind, it is to be expected in the aftermath of the truly tragic earthquake, tsunami and nuclear radiation problems in Japan that conspiracy theories will quickly take root and circulate rapidly. Some of the victims of these tragedies will derive a little comfort from focussing on the idea that their tribulations were actually designed and caused by one or more very bad people. A conspiracy theory that the earthquake and tsunami were deliberately caused by human action is entirely consistent with some elements of our understanding of human psychology. Dolphin (t) 05:38, 20 March 2011 (UTC)

It appears to be possible to induce very small earthquakes at a site by using injection wellbores to inject fluids. It can be a problem in oil and gas field development amongst other things. That's about it. Getting a fault to move by several metres over hundreds of kilometres of its length is a bit out of our league although I suppose it's theoretically possible in the same sense that dropping a copy of Yilmaz's Seismic Data Processing book out of a window in the middle of a city could, in prinicpal at least, make all of the buildings fall down if you were really very exceptionally unlucky... Sean.hoyland - talk 06:38, 20 March 2011 (UTC)

An explosion can cause seismic wave and water waves, which probably is the reasoning behind conspiracy theories. Not sure, though, if explosion can mimic devastation of earthquake and tsunami ~~Xil (talk) 10:59, 20 March 2011 (UTC)

The closest we can get to an artificial earthquake is to detonate a nuclear bomb underground, even this is of many orders of magnitude weaker than the earthquake that did happen in Japan. Besides, it's not something you can prepare and execute without drawing a lot of attention.

Some kind of "Tesla-earthquake-machine" present in some cheap science fiction or video games is completely absurd. The Earth is not of uniform density to allow waves to resonate enough, and even if such thing would be possible, it's utter nonsense to be the cause of the current events: such a thing would need a lot of resources, a lot of scientists working on it, which needs a huge infrastructure, a lot of people who support this infrastructure, then the whole international scientific community, all current ad future university professors and students who would find out what caused it, and soon we get to a point where millions of people would need to be involved in such a conspiracy all over the world, from every country. For such a conspiracy to remain a secret is completely implausible, even if the technology required for it would be possible, which I highly doubt. The problem with most conspiracy theorists is, that if what they believe has a 0.001% chance of being true, they regard it as proof of it being true.

Another "possibility" would be to deliberately not stop the reactor in time, but as in the above discussion, it would need millions upon millions of people from all over the world to be involved, so it's stupid to even consider it as a possibility.

Conspiracies can and do happen in the world, but they are mostly in the range of "bribe a politician to buy a property cheaper", or "manipulate the media to get a slightly better image of your company or ideology", or "steal some money by misusing legislative loopholes". To invent some completely new technology, or manipulate the currently existing highest technology, and hope no one will find out, is complete nonsense. --87.169.11.121 (talk) 15:51, 20 March 2011 (UTC)

A great deal of effort has been made to distinguish between earthquakes and underground explosions as part of monitoring the Test Ban Treaty using seismometers. Basically the computed focal mechanism shows whether the event involved movement on fault plane (producing the classic 'beachball plot') or was the result of an explosion (or in some cases an implosion such as in the collapse of old mine workings) where the plot is uniformly compressional (or tensional in the other case). Mikenorton (talk) 18:12, 20 March 2011 (UTC)

One of the top results of a Google search claims that the nuclear accident was much bigger than we believe it to be, and happened before the earthquake, killing many thousands, and irradiating even more. The whole tsunami was than artificially created as a cover-up, just to wash away the bodies, and to add to the realism, some agents were later planted as "survivors" to be rescued. The proof: so few bodies have been found, because the water washed away most of them.

The problem is, that there is no known technology to cause an earthquake this big, so the conspirators either managed to create, deploy and use it in a matter of hours, or they invested those horrible amounts of resources to build such an installation in the past, on the off chance that a nuclear meltdown might happen and than they could use that device to cover it up, while not using such groundbreaking new technology for anything else. --87.169.11.121 (talk) 18:54, 20 March 2011 (UTC)

That is an amazingly silly conspiracy theory. --Mr.98 (talk) 22:05, 20 March 2011 (UTC)

The energy of the recent earthquake in Japan was about 3x10²² joules. The largest nuclear bomb (and nuclear bombs are the closest we've ever got to making our own earthquakes) ever tested had an energy of about 2x10¹⁷ joules. That's more than 10,000 times smaller. There is no way we could create our own earthquake on that scale. I guess it might be possible to trigger an earthquake that would have happened sooner or later anyway. There have been proposals to try and do that before too much energy builds up so we can trigger a small, harmless earthquake instead of the very large earthquake we would get instead. However, no-one has come close to inventing a way to actually do that. --Tango (talk) 21:51, 20 March 2011 (UTC)

global warming

one big argument for nuclear power is it is better than coal for greenhouse gasses that cause "global warming," but what about all the excess "heat" that nuclear power releases plus the warming of the cool liquid used to keep the core cool? Isn't that contributing to global warming by definition, or has that already been considered in the comparison?98.221.254.154 (talk) 05:27, 20 March 2011 (UTC)

Nuclear fission does produce heat, just as coal does, but the concern about global warming comes from the carbon dioxide produced, not the initial heat produced. Carbon dioxide keeps sunlight from escaping Earth's atmosphere, reflecting it back toward the Earth's surface. So when you release CO2 into the air, it contributes to global warming via sunlight for as long as it is there. Nuclear fission does not produce CO2, so it doesn't really contribute to global warming.Aaron (talk) 05:51, 20 March 2011 (UTC)

Aaron's last sentence makes more sense as Nuclear fission does not produce CO2, so it doesn't really contribute to the Greenhouse effect. Greenhouse effect is retardation of the escape of heat from the Earth. Nuclear fission produces heat so it contributes to warming, but it doesn't produce CO2 so it doesn't contribute to the greenhouse effect. Dolphin (t) 07:03, 20 March 2011 (UTC)

Is there some way to relate the global warming effects of greenhouse gas emission to that of heat production? That is, how many joules of heat would I have to add to the atmosphere to bring about an equivalent warming to that caused by the release of one ton of CO2? -- 119.31.126.66 (talk) 08:19, 20 March 2011 (UTC)

Total global energy consumption is about 15 terawatts. The man-made effect of accumulated greenhouse gases is about 820 terawatts. So the man-made greenhouse effect is about 50 times the direct heating effect. Also, because greenhouse gases accumulate and have a long residence time in the atmosphere, that ratio is likely to increase over time. Dragons flight (talk) 08:42, 20 March 2011 (UTC)

Also any direct heating increases the amount of infrared radiation emitted by the earth's surface which has a cooling effect which substantially cancels the direct heating. That's why any direct heating is essentially negligible. Dauto (talk) 14:07, 20 March 2011 (UTC)

(It should be noted, of course, that while the act of fission releases no greenhouse gases, the full fuel cycle is not carbon neutral. It's just tremendously better, per megawatt of energy produced, than fossil fuels. It produces about .5-4% the CO₂ emissions as coal.[27]) --Mr.98 (talk) 15:34, 20 March 2011 (UTC)

May I suggest that the IAEA is not a particularly non-partisan source, and that any paper that starts with "the Uranium Institute (UI) decided to examine these claims and to attempt to refute them in more detail" is dubious as a scientific source. --Stephan Schulz (talk) 15:52, 20 March 2011 (UTC)

IAEA is a global independent organisation that reports to the UN. It's as unbiased as it gets. --85.77.43.229 (talk) 16:20, 20 March 2011 (UTC)

The numbers they cite look fairly legit to me. If you have better numbers, have at it. The real bait and switch here is obviously comparing it to coal and coal only — it would be more useful to compare it to things other than the dirtiest form of energy production we have. However I find it completely plausible that nuclear does pretty good when stacked up against coal when measured in terms of CO₂ emissions — or practically anything else. Coal is bad news. --Mr.98 (talk) 17:25, 20 March 2011 (UTC)

I don't think anybody needs to actually read that paper to realize that nuclear power produces much less Co2 than coal. Dauto (talk) 18:03, 20 March 2011 (UTC)

Expression for Thrust and Power coefficients

Hey, can anyone tell me the expression for Thrust Coefficient and Power Coefficient for a propeller in terms of Re, Mach Number and J ? Yes Michael? •^Talk 10:45, 20 March 2011 (UTC)

$T=C_{T}\rho n^{2}d^{4}$

$P=C_{P}\rho n^{3}d^{5}$

The relationship between these two coefficients and advance ratio J is shown graphically. I am looking at Chapter XI of Theory of Flight by Richard von Mises (1959), Dover Publications. This is now a very old book and I'm sure this information is available in all modern books on practical aerodynamics. Dolphin (t) 11:03, 20 March 2011 (UTC)

In Aerodynamics by L.J. Clancy (1975), Pitman Publishing Ltd, Section 17.3, there is also a definition of the Torque Coefficient, C_Q:

$Q=C_{Q}\rho n^{2}d^{5}$

Dolphin (t) 11:14, 20 March 2011 (UTC)

Well, I was looking for an expression for $C_{T}andC_{P}$ itself. Also, if there is an expression for Thrust by Torque, can you let me know? Yes Michael? •^Talk 11:32, 20 March 2011 (UTC)

These three coefficients vary with advance ratio in a way that is unique for any given design of propeller. There is not a mathematical relationship between coefficient and advance ratio, and the relationships must be determined empirically (ie by experiment) in the same way that the lift coefficient of a particular airfoil section varies with angle of attack and must be determined empirically. Firstly, determine exactly which propeller you want to consider, then go looking for three diagrams which show the relationship between advance ratio and each of the three coefficients for this propeller. Such diagrams will be available for a range of advance ratios from zero up to some maximum value, just as the lift coefficient of an airfoil can be shown on a diagram for a range of angles of attack from zero (or even negative) up to the stalling angle and a bit beyond.

Propeller manufacturers are likely to be reluctant to supply this information about their products, but all advanced text books about propellers should contain this information for at least one design of propeller. Dolphin (t) 21:47, 20 March 2011 (UTC)

Flat roof vs. sloped roof

Where is each of the options necessary? Can you have a flat roof in places where it snows?

Snow ifself is not an absolute showstopper. If only the snow melts in the summer, all you need to do is make the roof construction strong enough to carry the weight of one winter's worth of snowfall.

Liquid water is much more of a problem. Even slight deviations from perfect flatness will make rainwater (or meltwater) stand in shallow pools on the roof instead of running off, and it's hard to construct a roof surface that is watertight enough not to be damaged by this in the long run -- especially if temperatures reach freezing in the winter.

Anecdotally, flat roofs were popular in Denmark abound 1970, but most of them have since been overbuilt with peaked roofs due to recurring water damage. –Henning Makholm (talk) 15:06, 20 March 2011 (UTC)

OR: We have a flat roof in southern Ontario (Canada) where we get a lot of winter snow and a lot of days below freezing. Parts of the tar-and-gravel roof are 30 years old and parts only about 5 years old. We had one problem with a leak along one seam when storms came driving out of the east. It was repaired with an overlay of tar. Aside from that, we are warm and dry. The norm, however, is a pitched roof in such climates. Bielle (talk) 15:16, 20 March 2011 (UTC) P.S. Almost all commercial buildings of whatever floor area or height have flat roofs, and it is a rare one (though it does happen) that collapses under a snow load or leaks. Bielle (talk) 15:24, 20 March 2011 (UTC)

One factor seems to be the width of the building (by width I mean the direction in which the roof would have an elevation difference, if sloped, which is usually the narrowest dimesnion). The wider the roof, the higher it has to be, if sloped, so snow will tumble off. This means the material required varies roughly with the square (width×height) of the width. (It just varies linearly with the length, as expected.) So, if a building is 10x as wide, a sloped roof would take 100x as much material, cost 100x as much, etc. This quickly makes sloped roofs impractical for large buildings (an exception being perhaps the pyramids, where the roof and the building are one in the same ?). StuRat (talk) 19:16, 20 March 2011 (UTC)

As StuRat says, for a building of significant width, say more than 80 feet (24 m), one finds that the volume of structure for an appreciable slope becomes expensive. Multiple adjoining sloped roofs have issues with snow and water retention in the valleys that tend to discourage the use of that configuration. Simple sloped roofs are in general less vulnerable to leakage, since water doesn't linger. However, nobody nowadays designs a "flat" roof - there's always a modest slope to encourage drainage, although it may not be obvious on casual examination. Acroterion (talk) 22:09, 20 March 2011 (UTC)

Birdsong, UK

Yesterday in the suburbs and the countryside of south-eastern England I heard a lot of bird calls similar to this: Low-High-Low-High-Low-High-Low-High. Different birds sang between four and nine notes, all done quickly and without any pause in between the notes. The notes sounded more like something being plucked or twanged rather than whistled.

Is this sufficient to identify a particular species, or are there several species that sound similar? Is there anything like a Flora for birdsong? Thanks 92.28.241.202 (talk) 16:08, 20 March 2011 (UTC)

Basically this is the call of the Tit species. Great Tits sound like "teacher, teacher". The smaller tits call higher and quicker. --TammyMoet (talk) 16:57, 20 March 2011 (UTC)

Thanks, the song description matched. I did not realise there were so many of them. Perhaps they have been eating the bees. Does anyone know which are the commonest tit species in SE England? 92.28.241.202 (talk) 17:05, 20 March 2011 (UTC)

I suspect the blue tit is the commonest in SE England, but populations can fluctuate wildly from year to year. By the way, there are a number of websites where you can check out bird songs. This is one.--Shantavira|^{feed me} 18:01, 20 March 2011 (UTC)

From the great link of Shantavira, it must have been a great tit. 92.28.241.202 (talk) 19:35, 20 March 2011 (UTC)

Why do old AA batteries appear to sweat?

I've often found that old batteries in transistor radios etc are often covered in tiny drops of clear fluid, like sweat. The batteries that I've just looked at are metal-covered alkali batteries, so the "sweat" may be simply condensation. But very old zinc-carbon batteries often appear to have moisture underneath their plastic sleeve.

Why do batteries appear to sweat? Thanks 92.28.241.202 (talk) 16:57, 20 March 2011 (UTC)

Probably because they build up deposits of some sort of salt, which draws moisture out of the air, especially if you live in a very humid place such as Great Britain. Looie496 (talk) 17:42, 20 March 2011 (UTC)

Thanks, but GB is not a "very humid place" as our American chums seem to believe. Fogs are infrequent or rare. 92.28.241.202 (talk) 18:23, 20 March 2011 (UTC)

Oh please. I live in Britain, and it is indeed a damp, humid place most of the time. It has lower precipitation rates than many places in the USA, but it spreads them out over many days so we get days of mist, drizzle and, yes, fog. Fogs are not infrequent, especially in the cooler part of the year in the early morning and evening. We get river-mist here most mornings. How are our houses traditionally built? With sloping roofs that protrude past the walls, and with gutters when people can afford them. Because of all the rain. Recent improvements? Cavity walls anywhere even slightly exposed, because of all the rain and drizzle that gets driven against the walls by the wind. We have damp coursing as standard, and basements are rare. Mould and damp are common in certain parts of houses, because we live in a damp country. It is humid here most of the time: it is considered noteworthy when it is warm and dry, and people get over-excited.

This is why we were good at growing corn for the Romans. This is why we did so well at wool manufacture. This is probably why your batteries behave this way. Unless you live somewhere with a specially dry microclimate? 86.164.66.59 (talk) 19:42, 20 March 2011 (UTC)

Your experience is very different from mine - where are you? What you describe sounds like an extreme exaggeration. (I detect the Northern/Midlands mantra of "We're miserable, and it's all your (comfy southerners) fault!) You must be living in one the wettest parts of the country, somewhere like Manchester or the Lake District, or Scotland. In London its about 20 inches of precipitation a year. Its hardly a rain forest, and has less rain that most parts of europe or the western side of the US. Corn needs a dry climate to ripen by the way - as far as I understand it will not grow in Scotland, hence the oats. Wool thread manufacture was purposedly done in a damp rainy part of the country. You forgot to mention the mushrooms growing out of the carpet, lol. 92.28.241.202 (talk) 20:05, 20 March 2011 (UTC)

This image of unclear provenance seems to support the claim that London is a humid place. It's true that London is not very foggy. According to Wikipedia, London fog was pea soup fog, which is actually smog, and disappeared with the end of the coal-burning era. -- BenRG (talk) 20:44, 20 March 2011 (UTC)

I agree that in mid-winter it may be more humid than it is in most parts of North America, the reason being because in England its above freezing most of the time, and so the water vapour in the air does not freeze into snow etc. 92.15.21.23 (talk) 22:20, 20 March 2011 (UTC)

That humidity scale is grossly exaggerated. Where I am now, the humidity is only 42%, which is fairly typical. Its 42% indoors: outdoors it would be less. "Mould and damp are common in certain parts of houses" says our friend above - rubbish! Only if you are living in a cave or a slum. According to that image, a "wet day" is a day with more than 0.1mm of precipitation - you would have great difficulty measuring a tenth of a millimetre. I think that image is a fraud, as it also says that the hottest temperature is only about 60 degrees farehnheit in the summer ...... hey, is this London, Canada? Very funny. 92.15.21.23 (talk) 21:49, 20 March 2011 (UTC)

Who in Britian can't afford gutters? They are just a few bits of plastic... --Tango (talk) 22:03, 20 March 2011 (UTC)

See Alkaline battery#Leaks Potassium hydroxide electrolyte can leak out of old alkaline batteries. When it dries it can leave a white residue I would expect electrolyte leakage is the source of moisture on an old failed alkaline battery, rathre than condensation of atmospheric moisture, unless the battery was brought into a moist place from a cold place. Carbon zinc batteries were worse in this respect in terms of destroying an device when the batteries were left in it too long. Edison (talk) 20:00, 20 March 2011 (UTC)

"This is why we were good at growing corn for the Romans.": your assertion is ridiculous. The Roman didn't know corn until the XVI century, when there were not Romans anymore... 212.169.178.75 (talk) 22:55, 20 March 2011 (UTC)

About duck being a red meat...

With all the current hoopla about the risks of red meat, I'm trying to determine if duck is counted as one for the purposes of said elevated health risks. The article about red meat is unclear here... Egg Centric 18:52, 20 March 2011 (UTC)

That's a good question, and I agree that the article may be contradictory. It says that red meat includes 'duck' but then goes on to talk about a bunch of health risks associated with 'red meat' when in fact the studies may or may not have included duck. What you'd have to do is go to the studies themselves. 220.244.35.181 (talk) 19:16, 20 March 2011 (UTC)

Red meat is a phrase that was invented and pushed by the beef industry to refer to "beef" whenever health risks of eating beef are discussed. Thus, when beef is bad for you, it is called "red meat", but when beef is good for you, it is called "beef". Sort of a form of reverse marketing, so in your mind, you don't associate beef with unhealthy qualities. Duck does not fit into the "Standard" American triumverate of meat protein (Beef, Pork, and Chicken), so I am not sure that most people would think of duck as being substantially different from Chicken, excepting that ALL duck is, culinarily and probably nutritionally, closer to "dark meat chicken" (i.e. lower quarters, thigh and leg), even duck breast is more like chicken legs than anything. Whiter meats (including chicken breast meat, turkey breast meat, and some parts of the pork, like the loin and the tenderloin) are lower in fat, so for people who care about fat intake, they advise people to stick to "whiter" meats. Also, with regard to duck being "red meat", it can be culinarily treated more like "beef" than "chicken", so for example, duck is still tasty when cooked to "medium rare", like beef is, but unlike chicken where "medium rare" chicken is disgusting. Nutritionally, however, I don't know that duck is distinctly more like beef or chicken. --Jayron32 22:35, 20 March 2011 (UTC)

Potassium Iodide

Would it be bad to store potassium iodide in water? I diluted potassium iodide (SSKI) in water, would it make the shelf like any less or would it make it less effective if it was stores like this overtime? —Preceding unsigned comment added by 76.169.33.234 (talk) 20:54, 20 March 2011 (UTC)

Potassium iodide is fully soluble, highly stable, and not likely to be a food source for any microbes. In other words, I can't see anything happening to it whether it is in solution or solid form. In either solution or solid form, it should outlive all of us. --Jayron32 22:26, 20 March 2011 (UTC)

Sea kelp and iodine

If I have sea kelp that says it has 0.06% iodine, how much would I have to take for it to be equivalent to 100mg of iodine which is what I read is equivalent to the amount of iodine in a 130mg tablet of potassium iodine pill? Thanks —Preceding unsigned comment added by 76.169.33.234 (talk) 21:01, 20 March 2011 (UTC)

0.06% of what? Is it 0.06% of the total mass of the seakelp or 0.06% of the Recommended Daily Allowance of iodine for an adult human? If it is the former, you would need to eat 100mg/.0006 = 16,667 mg or 16.667 grams. If it is the latter, you would first need to know what the RDA for iodine was... --Jayron32 22:24, 20 March 2011 (UTC)

You shouldnt take any iodine, unless you are in Japan close to the reactors. See http://www.bbc.co.uk/news/health-12784774 92.15.21.23 (talk) 22:33, 20 March 2011 (UTC)

Not to be pendandic, but this conversation should be about iodide, not iodine. If you are considering consuming them, mixing up the two could be dangerous. 71.185.49.174 (talk) 22:40, 20 March 2011 (UTC)

Tidal energy from the Wash and the Severn

How many typical nuclear power stations would harnessing the tides of the Wash and Severn be equivalent to? 92.15.21.23 (talk) 22:01, 20 March 2011 (UTC)

It would depend on the placement of the barrages and also which types of nuclear power stations you wish to compare them to. For instance, the proposed Severn Barrage may generate from 0.75-15GW depending on which plan you read. The proposed Hinkley Point C nuclear power station could produce 1.6GW. Nanonic (talk) 22:21, 20 March 2011 (UTC)

The 15GW figure is peak power, which isn't terribly informative when you're costing it, compared with a source with a fairly steady rate. Unfortunately the article isn't very good at giving idea (beyond the rough "average" numbers below) as to how long a given barrier would spend delivering power at that level, at the average level, and at lower levels. -- Finlay McWalter ☻ Talk 22:31, 20 March 2011 (UTC)

There are many different proposals for designs for a Severn Barrage, with quite a range of costs, power levels, and impacts. Looking at that article, the 1987 proposal would generate 313 MW on average, the 1989 design 2,000 MW on average. If you compare that to Torness Nuclear Power Station, the most productive of the UK's Advanced gas-cooled reactors, which produces at 1250 MW over two reactors. the Severn Barrage article, using those 1989 figures, puts the yield at 3 reactors worth, and observes that the estimated cost is "about the same as six nuclear reactors, but different lifespan". If Torness serves its planned 35 years of service, you'd expect a Barrage of the 1989 design to pass nuclear at some age shy of 70 years. But that's a hopelessly simplistic calculation: on the nuclear side it doesn't count the comparative cost of operating and maintaining both plants, and the cost of the fuel cycle; on the tidal side it doesn't count the (presumably fairly low) running and maintenance cost, or the (difficult to put into numbers, but not trivial) cost of the environmental impact the barrier would bring. So, handwaving a bit, power yield of 1 1/2 nuclear stations, more expensive in the short term but cheaper in the long term. -- Finlay McWalter ☻ Talk 22:24, 20 March 2011 (UTC)

I hate this "environmental impact" twaddle - who cares about a few ducks. 92.15.21.23 (talk) 22:30, 20 March 2011 (UTC)

Chernobyl vs Deepwater Horizon

In terms of environmental damage (both present and predicted by environmentalists), how does the Deepwater Horizon incident compare to Chernobyl? Thanks. 72.128.95.0 (talk) 23:06, 20 March 2011 (UTC)